Content
2008
The persisting challenge of selective and specific proteasome inhibition
24.12.2008
J. Pep. Sci.,
2009,
15(2),
58-66, doi:10.1002/psc.1107
published on 24.12.2008
Journal of Peptide Science, online article
Journal of Peptide Science, online article
Since the discovery of the proteasome and its structure elucidation intensive research programs in academic institutions and pharmaceutical industries led to identification of a wide spectrum of synthetic and natural small proteasomal inhibitors. Activity studies with these small molecules helped to deeply understand the complex biochemical organization and functioning of the proteasome. The new structural and biochemical insights placed the proteasome as an important anti-cancer drug target, as revealed by the dipeptide boronate proteasome inhibitor, bortezomib, which is currently used for treatment of multiple myeloma. Serious side effects and partial cell resistance against bortezomib demand creation and discovery of new improved generations of more specific and potent proteasomal inhibitors.
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Aggregation and Reactivity of Organozincate Anions Probed by Electrospray Mass Spectrometry
15.12.2008
Organometallics,
2008,
DOI: 10.1021/om8007037,
published on 15.12.2008
Organometallics, online article
Organometallics, online article
Electrospray ionization (ESI) of mixtures of organolithium compounds and zinc chloride in tetrahydrofuran produced manifold mono- and polynuclear organozincate anions. Formation of the latter is strongly favored by the incorporation of chloride ligands, which apparently adopt bridging binding modes. Analysis of LinBu/ZnCl2 solutions at different concentrations showed that the relative ESI signal intensities for anions in different aggregation states closely correlate with their expected equilibria in
solution. Moreover, the uni- and bimolecular gas-phase reactivity of the mass-selected anionic organozincates was studied. Upon collision-induced dissociation, most of these complexes lose a neutral metal fragment, and only the tributylzincates ZnBu3 - react by elimination of alkenes. The tributylzincate complexes were also found to undergo ion-molecule reactions with formic acid. The relative rates for these proton-transfer processes decrease in the series ZnnBu3-, ZnsBu3-, and ZntBu3-, and they also decrease if the butyl groups are substituted for chloride ligands. These trends fully agree with the known solution-phase chemistry of organozinc compounds.
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Recognition and repair of UV lesions in loop structures of duplex DNA by DASH-type cryptochrome
12.12.2008
DNA photolyases and cryptochromes (cry) form a family of flavoproteins that use light energy in the blue/UV-A region for the
repair of UV-induced DNA lesions or for signaling, respectively.
Very recently, it was shown that members of the DASH cryptochrome
subclade repair specifically cyclobutane pyrimidine dimers (CPDs) in UV-damaged single-stranded DNA. Here, we report the
crystal structure of Arabidopsis cryptochrome 3 with an in-siturepaired CPD substrate in single-stranded DNA. The structure
shows a binding mode similar to that of conventional DNA photolyases. Furthermore, CPD lesions in double-stranded DNA are
bound and repaired with similar efficiency as in single-stranded
DNA if the CPD lesion is present in a loop structure. Together, these
data reveal that DASH cryptochromes catalyze light-driven DNA repair like conventional photolyases but lack an efficient flipping mechanism for interaction with CPD lesions within duplex DNA.
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Identification of potential substrate proteins for the periplasmic Escherichia coli chaperone Skp
08.12.2008
The “seventeen kilodalton protein” (Skp) is a predominant periplasmic chaperone of Escherichia
coli, which is involved in the biogenesis of abundant outer membrane proteins (OMPs) such as OmpA, PhoE, and LamB. In this study the substrate profile of Skp was investigated in a proteomics approach. Skp was overexpressed in a deficient E. coli strain as a fusion protein with the Strep–tag and captured, together with any host proteins associated with it, from the periplasmic cell extract under mild conditions via one-step Strep–Tactin affinity chromatography. Copurified
substrate proteins were then identified by high resolution 2-DE with immobilized pH-gradients,
followed by MALDI-TOF MS. Apart from the known Skp substrates, including OmpA and LamB, more than 30 other interacting proteins were detected, especially from the outer membrane, among these FadL and BtuB, and from the periplasm such as MalE and OppA. Thus, Skp does not only serve as a specialized chaperone for a small set of OMPs, but it seems to exhibit a broader substrate spectrum, including soluble periplasmic proteins. These findings should
prompt further investigation into the physiological role of Skp and may promote its use for the bacterial production of biochemically active heterologous proteins whose folding requires secretion into the oxidizing milieu of the periplasm.
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A Human snoRNA with MicroRNA-Like Functions
21.11.2008
Small noncoding RNAs function in concert with Argonaute
(Ago) proteins to regulate gene expression at
the level of transcription, mRNA stability, or translation.
Ago proteins bind small RNAs and form the
core of silencing complexes. Here,wereport the analysis
of small RNAs associated with human Ago1 and
Ago2 revealed by immunoprecipitation and deep
sequencing. Among the reads, we find small RNAs
originating from the small nucleolar RNA (snoRNA)
ACA45. Moreover, processing of ACA45 requires
Dicer activity but is independent of Drosha/DGCR8.
Using bioinformatic prediction algorithms and luciferase
reporter assays, we uncover the mediator subunit
CDC2L6 as one potential mRNA target of ACA45
small RNAs, suggesting a role for ACA45-processing
products in posttranscriptional gene silencing. We
further identify a number of human snoRNAs with
microRNA (miRNA)-like processing signatures. We
have, therefore, identified a class of small RNAs in
human cells that originate from snoRNAs and can
function like miRNAs.
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Novel Diazirine-Containing DNA Photoaffinity Probes for the Investigation of DNA-Protein-Interactions
14.11.2008
An investigation of the precise interactions between damaged
DNA and DNA repair enzymes is required in order to understand
the lesion recognition step, which is one of the most fundamental
processes in DNA repair. Most recently, photoaffinity labeling
approaches have enabled the analysis of even transient protein-
DNA interactions. Here we report the synthesis and evaluation of
oligonucleotides that contain two photoaffinity “catcher moieties”
next to incorporated DNA lesions. With these DNA constructs
it is possible to analyze the interactions between DNA lesions
and the appropriate repair enzymes. The probes labeled the
repair protein efficiently enough to enable subsequent protein
analysis by mass spectrometry.
Evidence for Insertional RNA Editing in Humans
06.11.2008
Large-scale analysis directly at the protein level holds the promise of uncovering features not apparent or present at the gene level [1,2,3]. Although mass spectrometry (MS)-based proteomics can now identify and quantify thousands of cellular proteins in large-scale proteomics experiments, much of the peptide information contained in these experiments remains unassigned [4]. Here, we use such information to discover a previously unreported mechanism creating altered protein forms. Linker histones H1 and high-mobility group (HMG) proteins are abundant nuclear proteins that regulate gene expression through modulation of chromatin structure [5,6,7,8]. In the high-resolution MS analysis of histone H1 and HMG protein fractions isolated from human cells, we discovered peptides that mapped upstream of the known translation start sites of these genes. No alternative upstream start site exists in the genome, but analysis of Expressed Sequence Tag (EST) databases revealed that these N-terminally extended (ET) proteins are due to in-frame translation of the 5′ untranslated region (5′UTR) sequences of the transcripts. The new translation start sites are created by a single uridine insertion between AG, reflecting a previously unreported RNA-editing mechanism. To our knowledge, this is the first report of RNA-insertion editing in humans and may be an example of the type of discoveries possible with modern proteomics methods.
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5'-triphosphate-siRNA: turning gene silencing and Rig-I activation against melanoma
02.11.2008
Genetic and epigenetic plasticity allows tumors to evade single-targeted treatments. Here we direct Bcl2-specific short interfering RNA (siRNA) with 5¢-triphosphate ends (3p-siRNA) against melanoma. Recognition of 5¢-triphosphate by the cytosolic antiviral helicase retinoic acid–induced protein I (Rig-I, encoded by Ddx58) activated innate immune cells such as dendritic cells and directly induced expression of interferons (IFNs) and apoptosis in tumor cells. These Rig-I–mediated activities synergized with
siRNA-mediated Bcl2 silencing to provoke massive apoptosis of tumor cells in lung metastases in vivo. The therapeutic activity required natural killer cells and IFN, as well as silencing of Bcl2, as evidenced by rescue with a mutated Bcl2 target, by sitespecific cleavage of Bcl2 messenger RNA in lung metastases and downregulation of Bcl-2 protein in tumor cells in vivo. Together, 3p-siRNA represents a single molecule–based approach in which Rig-I activation on both the immune- and tumor cell level corrects immune ignorance and in which gene silencing corrects key molecular events that govern tumor cell survival.
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Complex patterns of histidine, hydroxylated amino acids and the GxxxG motif mediate high-affinity transmembrane domain interactions
30.10.2008
Journal of Molecular Biology,
2009,
385, 3,
912 - 923
published on 30.10.2008
Journal of Molecular Biology, online article
Journal of Molecular Biology, online article
Specific interactions of transmembrane helices play a pivotal role in the folding and oligomerization of integral membrane proteins. The helix–helix interfaces frequently depend on specific amino acid patterns. In this study, a heptad repeat pattern was randomized with all naturally occurring amino acids to uncover novel sequence motifs promoting transmembrane domain interactions. Self-interacting transmembrane domains were selected from the resulting combinatorial library by means of the ToxR/POSSYCCAT system. A comparison of the amino acid composition of high-and low-affinity sequences revealed that high-affinity transmembrane domains exhibit position-specific enrichment of histidine. Further, sequences containing His preferentially display Gly, Ser, and/or Thr residues at flanking positions and frequently contain a C-terminal GxxxG motif. Mutational analysis of selected sequences confirmed the importance of these residues in homotypic interaction. Probing heterotypic interaction indicated that His interacts in trans with hydroxylated residues. Reconstruction of minimal interaction motifs within the context of an oligo-Leu sequence confirmed that His is part of a hydrogen bonded cluster that is brought into register by the GxxxG motif. Notably, a similar motif contributes to self-interaction of the BNIP3 transmembrane domain.
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Crystal Structure and Mechanism of a DNA (6-4) Photolyase
27.10.2008
Angew. Chem. Int. Ed.,
2008,
47,
10.1002/anie.200804268
published on 27.10.2008
Angewandte Chemie Int. Ed., online article
Angewandte Chemie Int. Ed., online article
UV irradiation of cells gives rise to the formation of cyclobutane
pyrimidine dimers (CPD) and so-called (6-4) DNA lesions (Scheme 1). Both lesions are major photoproducts formed in dipyrimidine sequences of double-stranded DNA. Repair of these lesions is essential because of their high mutagenic potential. Particularly important in many organisms are the photolyase-mediated repair systems that are able to split CPD lesions and (6-4) lesions directly back into their corresponding monomers. While formation and photolyase repair of CPD lesions is well studied, little is known about (6-4) lesions. In particular, the mechanism of repair of the (6-4) lesions by (6-4) DNAphotolyases is a longstanding question. Currently it is believed that the enzyme rearranges the (6-4) lesion with the help of two conserved histidine residues in the active site to form an oxetane intermediate (Scheme 1), which is split after single-electron donation from a light-activated FADH. We report here the first crystal structures of a (6-4) DNA photolyase enzyme.
The structures show the enzyme in complex with a (6-4) lesion
containing DNAbefore and after in situ repair. Based on the
structural and biochemical data we propose a modified repair
mechanism that lacks the strained oxetane intermediate.
Structural determinants of MIF functions in CXCR2-mediated inflammatory and atherogenic leukocyte recruitment
21.10.2008
We have recently identified the archaic cytokine macrophage migration inhibitory factor (MIF) as a non-canonical ligand of the CXC chemokine receptors CXCR2 and CXCR4 in inflammatory and
atherogenic cell recruitment. Because its affinity for CXCR2 was particularly high, we hypothesized that MIF may feature structural motives shared by canonical CXCR2 ligands, namely the conserved
N-terminal Glu-Leu-Arg (ELR) motif. Sequence alignment and structural modeling indeed revealed a pseudo-(E)LR motif (Asp-44-XArg-11) constituted by non-adjacent residues in neighboring loops
but with identical parallel spacing as in the authentic ELR motif. Structure–function analysis demonstrated that mutation of residues R11, D44, or both preserve proper folding and the intrinsic catalytic property of MIF but severely compromises its binding to CXCR2 and abrogates MIF/CXCR2-mediated functions in chemotaxis and arrest of monocytes on endothelium under flow conditions. R11A-MIF and the R11A/D44A-MIF double-mutant exhibited a pronounced defect in triggering leukocyte recruitment to early atherosclerotic endothelium in carotid arteries perfused ex vivo
and upon application in a peritonitis model. The function of D44A-MIF in peritoneal leukocyte recruitment was preserved as a result of compensatory use of CXCR4. In conjunction, our data identify a pseudo-(E)LR motif as the structural determinant for MIF’s activity as a non-canonical CXCR2 ligand, epitomizing the
structural resemblance of chemokine-like ligands with chemokines and enabling selective targeting of pro-inflammatory MIF/CXCR2 interactions.
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Leaving Groups Prolong the Duration of 20S Proteasome Inhibition and Enhance the Potency of Salinosporamides
21.10.2008
J. Med. Chem.,
2008,
51 Issue 21,
6711-24
published on 21.10.2008
Journal of Medicinal Chemistry, online article
Journal of Medicinal Chemistry, online article
Salinosporamide A (1 (NPI-0052)) is a potent, monochlorinated 20S proteasome inhibitor in clinical trials for the treatment of cancer. To elucidate the role of the chlorine leaving group (LG), we synthesized analogues with a range of LG potentials and determined their IC50 values for inhibition of chymotrypsin-like (CT-L), trypsin-like (T-L), and caspase-like (C-L) activities of 20S proteasomes. Proteasome activity was also determined before and after attempted removal of the inhibitors by dialysis. Analogues bearing substituents with good LG potential exhibited the greatest potency and prolonged duration of proteasome inhibition, with no recovery after 24 h of dialysis. In contrast, activity was restored after e12 h in the case of non-LG analogues. Intermediate results were observed for fluorosalinosporamide, with poor LG potential. Kinetic studies indicate that 1 acts as a classical slow, tight inhibitor of the CT-L, T-L, and C-L activities and that inhibition occurs via a two-step mechanism involving reversible recognition followed by rate-limiting formation of a covalent enzyme-inhibitor complex.
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Azatryptophans endow proteins with intrinsic blue fluorescence
21.10.2008
Our long-term goal is the in vivo expression of intrinsically colored
proteins without the need for further posttranslational modification
or chemical functionalization by externally added reagents.
Biocompatible (Aza)Indoles (Inds)/(Aza)Tryptophans (Trp) as optical
probes represent almost ideal isosteric substitutes for natural
Trp in cellular proteins. To overcome the limits of the traditionally
used (7-Aza)Ind/(7-Aza)Trp, we substituted the single Trp residue
in human annexin A5 (anxA5) by (4-Aza)Trp and (5-Aza)Trp in
Trp-auxotrophic Escherichia coli cells. Both cells and proteins with
these fluorophores possess intrinsic blue fluorescence detectable
on routine UV irradiations. We identified (4-Aza)Ind as a superior
optical probe due to its pronounced Stokes shift of 130 nm, its
significantly higher quantum yield (QY) in aqueous buffers and its
enhanced quenching resistance. Intracellular metabolic transformation of (4-Aza)Ind into (4-Aza)Trp coupled with high yield
incorporation into proteins is the most straightforward method for
the conversion of naturally colorless proteins and cells into their
blue counterparts from amino acid precursors.
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Structural Analysis of Spiro b-Lactone Proteasome Inhibitors
17.10.2008
J. Am. Chem. Soc.,
2008,
130 (45),
14981-3
published on 17.10.2008
J. Am. Chem. Soc., online article
J. Am. Chem. Soc., online article
Spiro β-lactone-based proteasome inhibitors were discovered in the context of an asymmetric catalytic total synthesis of the natural product (+)-lactacystin (1). Lactone 4 was found to be a potent inhibitor of the 26S proteasome, while its C-6 epimer (5) displayed weak activity. Crystallographic studies of the two analogues covalently bound to the 20S proteasome permitted characterization of the important stabilizing interactions between each inhibitor and the proteasome’s key catalytic N-terminal threonine residue. This structural data support the hypothesis that the discrepancy in potency between 4 and 5 may be due to differences in the hydrolytic stabilities of the resulting acyl enzyme complexes.
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CIPSM-Researchers Stephan Sieber and Thomas Böttcher win the Innovation award 2008 of the BioRegions in Germany
14.10.2008
published on 14.10.2008
BIONRM
BIONRM
The winners of the second ever Innovation Award of the German BioRegions were announced on the 7th October – Thomas Böttcher together with Dr. Stephan Sieber from CIPSM were awarded joint prizes by Director General from the German Federal Ministry of Education and Research together with Dr. Heinz Bettmann, BioCologne e.V. representing this year’s sponsors.
The ceremony took place as a highlight of the Biopolitics Conference. This conference is part of the programme for this year’s BIOTECHNICA, the leading fair for European biotechnology in Hanover. After the award ceremony, the winners presented their research projects to the specialist audience at the Innovation Forum.
The Innovation Award pays tribute to outstanding patents from the life sciences with high innovation and market potential. This year, the award went to projects from the areas of molecular cell differentiation, chemical microbiology, and malaria research.
“Technology transfer is one of the bioregions’ main tasks. Not only do we aim to draw attention to particularly exciting projects, but we also aim to support their implementation with our Innovation Award,” said Dr. Kai Uwe Bindseil, head of BioTOP Berlin-Brandenburg and spokesman of the BioRegions working group.
This year, individual scientists and research groups from all over Germany have submitted their proposals. “We were impressed by the quality and diversity of the projects. This is a good sign and reflects the high level of research”, said Dr. Erika Sahrhage of BIO-OWL e.V, who also spoke on behalf of Uwe Seidel of BioIndustry e.V. Sahrhage and Seidel were the coordinators of this year’s Innovation Award.
Financial support for the Innovation Award was provided by Deutsche Messe AG, BioCologne e.V., and Grund Intellectual Property Group in Munich.
Thomas Böttcher is working on his PhD in Dr. Stephan Sieber’s lab at CIPSM in Munich in the area of chemical microbiology. Within the framework of his PhD thesis, he developed a technique to identify cellular targets of beta-lactones in bacteria in order to investigate molecular mechanisms of action. A key regulator of the virulence of pathogenic bacteria was found, which is decisive not for the survival but rather for their pathogenic impact of the bacteria. The Innovation Award pays tribute to the work of both researchers, which has demonstrated that beta-lactones are a potentially promising starting point for tailor-made therapies aiming to treat diseases and their pathogens which are resistant to conventional antibiotics.
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Beta-Lactones as Specific Inhibitors of ClpP Attenuate the Production of Extracellular Virulence Factors of Staphylococcus aureus
11.10.2008
Journal of the American Chemical Society,
2008,
DOI: 10.1021/ja8051365j,
published on 11.10.2008
JACS, online article
JACS, online article
With the evolution of multidrug resistant bacterial pathogens,
infectious diseases pose once again a serious threat to public health. Especially the opportunistic pathogen Staphylococcus aureus has gained importance through the dramatically increasing appearance of methicillin-resistant (MRSA) strains in hospitals and the recent emergence of epidemic community-associated MRSA infections. Major reasons for this daunting problem are the excessive use of conventional antibiotics, the limited number of essential cellular targets addressed by these compounds, and their paramount selective pressure exerted on bacterial viability leading to resistance development. Here we introduce an alternative strategy based on functionalized beta-lactones to target bacterial virulence rather than viability.
A central role in S. aureus virulence regulation can be attributed
to the caseinolytic protein protease (ClpP), a phylogenetically highly conserved serine protease that was found to be crucial for virulence of many bacterial pathogens.
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Postsynthetic DNA Modification through the Copper-Catalyzed Azide–Alkyne Cycloaddition Reaction
22.09.2008
Angew. Chem. Int. Ed.,
2008,
47 Issue 44,
8350-8
published on 22.09.2008
Angewandte Chemie Int. Ed., online article
Angewandte Chemie Int. Ed., online article
The attachment of labels onto DNA is of utmost importance in many areas of biomedical research and is valuable in the construction of DNA-based functional nanomaterials. The copper(I)-catalyzed Huisgen cycloaddition of azides and alkynes (CuAAC) has recently
been added to the repertoire of DNA labeling methods, thus allowing the virtuallyunlimited functionalization of both small synthetic
oligonucleotides and large gene fragments with unprecedented efficiency. The CuAAC reaction yields the labeled polynucleotides in very high purityafter a simple precipitation step. The reviewed technology is currentlych anging the wayin which functionalized DNA strands are generated cost-efficientlyin high qualityfor their application in molecular diagnostics systems and nanotechnological research.
The 1.8-Å Crystal Structure of α1-Acid Glycoprotein (Orosomucoid) Solved by UV RIP Reveals the Broad Drug-Binding Activity of This Human Plasma Lipocalin
16.09.2008
α1-Acid glycoprotein (AGP) is an important drug-binding protein in human plasma and, as an acute-phase protein, it has a strong influence on pharmacokinetics and pharmacodynamics of many pharmaceuticals. We report the crystal structure of the recombinant unglycosylated human AGP at 1.8 Å resolution, which was solved using the new method of UVradiation-
damage-induced phasing (UV RIP). AGP reveals a typical
lipocalin fold comprising an eight-stranded β-barrel. Of the four loops that form the entrance to the ligand-binding site, loop 1, which connects β- strands A and B, is among the longest observed so far and exhibits two full turns of an α-helix. Furthermore, it carries one of the five N-linked glycosylation sites, while a second one occurs underneath the tip of loop 2. The branched, partly hydrophobic, and partly acidic cavity, together with the presumably flexible loop 1 and the two sugar side chains at its entrance, explains the diverse ligand spectrum of AGP, which is known to vary with changes in glycosylation pattern.
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Beta-Lactams as Selective Chemical Probes for the in Vivo Labeling of Bacterial Enzymes Involved in Cell Wall Biosynthesis, Antibiotic Resistance, and Virulence
10.09.2008
Journal of the American Chemical Society,
2008,
DOI: 10.1021/ja803349j,
published on 10.09.2008
JACS, online article
JACS, online article
With the development of antibiotic-resistant bacterial strains, infectious diseases have become again a life-threatening problem. One of the reasons for this dilemma is the limited number and breadth of current therapeutic targets for which several resistance strategies have evolved over time. To expand the number of addressable enzyme targets and to understand their function, activity, and regulation, we utilized a chemical proteomic strategy, called activity-based protein profiling (ABPP) pioneered by Cravatt, for the identification of β-lactam-binding enzymes under in vivo conditions. In this two-tiered strategy, we first prepared a selection of conventional antibiotics for labeling diverse penicillin binding proteins (PBPs) and second introduced a new synthetic generation of β-lactam probes, which labeled and inhibited a selection of additional PBP unrelated bacterial targets. Among these, the virulence-associated enzyme ClpP and a resistance-associated β-lactamase were labeled and inhibited by selected probes, indicating that the specificity of β-lactams can be adjusted to versatile enzyme families with important cellular functions.
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Hier geht was!
10.09.2008
2008 is great!
Ein hochrangiger Wissenschaftler kündigt seine Stelle an der Eliteuniversität Berkeley, weil er lieber an einer deutschen Universität arbeiten möchte - und bringt auch gleich sein ganzes Forschungsteam mit.
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Intracellular uptake and inhibitory activity of aromatic fluorinated amino acids in human breast cancer cells
05.09.2008
Nonproteinogenic amino acids that either occur naturally or are
synthesized chemically are becoming important tools in modern
drug discovery. In this context, fluorinated amino acids have great potential in the development of novel pharmaceuticals and drugs. To assess whether different fluorinated aromatic amino acid analogues of phenylalanine, tyrosine, and tryptophan are potentially interesting as therapeutic drugs, we examined their
cytostatic and cytotoxic effects on the growth of the human breast cancer cell line MCF-7. Of all the tested analogues l-4-fluorotryptophan, l-6-fluorotryptophan and l-p-fluorophenylalanine effectively and irreversibly inhibited cell growth with IC50 values in the low micromolar range (3–15 mm). Additionally, using l-4- [14C]fluorotryptophan, and l-6-[14C]fluorotryptophan, we discovered that the cellular uptake of these fluorinated amino acids occurs through active transport with a 70-fold excess of intracellular over extracellular concentrations. We identified system L as the responsible amino acid transporter. Our findings fully support the idea that fluorinated aromatic amino acid analogues are promising chemotherapeutics with the potential for use in combination with classical cancer therapy, and as new cytotoxic drugs for certain tumor types such as melanoma.
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Convenient syntheses of homopropargylglycine
27.08.2008
An improved classic Strecker synthesis was elaborated leading to racemic homopropargylglycine (Hpg) in 61% overall yield, while an asymmetric Strecker reaction produced Hpg and the higher homolog 2-aminohept-6-ynoic acid in significantly higher yields and over 80% ee.
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Inhibition of transcription factors with small organic molecules
22.08.2008
Current Opinion in Drug Discovery & Development,
2008,
Vol 11/ No 5,
666-74
published on 22.08.2008
BioMed Central, online article
BioMed Central, online article
Protein-protein interactions regulate almost all aspects of cellular signaling and aberrant protein-protein interactions have the potential to cause or contribute to human disease. The modulation of these interactions by drug-like molecules would offer previously unavailable opportunities to explore the relevance of pre-selected protein-protein interactions for cellular signaling, as well as benefits to patients. After an initial period of skepticism with regards to feasibility, there is now an encouraging set of data indicating that the effective and selective modulation of protein-protein interactions by drug-like molecules is attainable. This review highlights selected areas of current research
that are aimed at identifying potent inhibitors of disease-relevant protein-protein interactions.
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Inhibition of transcription factors with small organic molecules
13.08.2008
Current Opinion in Chemical Biology,
2008,
doi:10.1016/j.cbpa.2008.07.023,
published on 13.08.2008
ScienceDirect, online article
ScienceDirect, online article
Gene-specific transcription factors are DNA binding proteins that function at the center of the transcriptional machinery to mediate the cellular phenotype in response to extracellular signals. Owing to the lack of enzymatic activities of these intracellular proteins, manipulating the activity of transcription factors by small organic molecules is widely considered to be a difficult task. In this review, I will discuss general approaches designed to inhibit a subset of transcription factors, referred to as dimeric transcription factors, by cell-permeable small organic molecules that inhibit protein–protein interactions or protein–DNA interactions. These dimeric transcription factors include hypoxia-inducible factor (HIF)-1, c-Myc, and signal
transducer and activator of transcription (STAT) 3. The data presented here indicate that dimeric transcription factors can be potently and selectively inhibited by drug-like small molecules.
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Exploiting Cross-Amyloid Interactions To Inhibit Insulin Aggregation but not Function: Nanomolar Affinity Inhibition of Insulin Aggregation by an IAPP Mimic
08.08.2008
Angewandte Chemie,
2008,
47,
10.1002/anie.200801499
published on 08.08.2008
Angewandte Chemie, online article
Angewandte Chemie, online article
In vivo protein aggregation is strongly linked to the pathogenesis of several incurable celland neurodegenerative diseases including Alzheimer’s disease (AD) and type II diabetes (T2D). In vitro protein aggregation leads to a loss of function and complicates therapeutic application of a number of bioactive proteins or polypeptides such as insulin. Designing potent inhibitors of aggregation of such proteins is however a difficult task as these
compounds should not affect protein function. Here we present a novel chemical strategy to generate inhibitors of protein aggregation that do not affect protein function by mimicking
natively occuring cross-amyloid peptide interactions. We exemplify the validity of this approach by demonstrating that IAPP-GI, a designed soluble and non-amyloidogenic mimic of islet amyloid polypeptide (IAPP), which is a native insulin interaction partner and a key amyloidogenic polypeptide of T2D, is a nanomolar affinity inhibitor of non-native aggregation of insulin without affecting its biological function. As IAPP-GI also blocks with nanomolar activity cytotoxic aggregation of both IAPP and the key amyloidogenic peptide of AD Aβ, it could become a unique lead compound for the development of novel therapeutic strategies targeting both AD and T2D. In addition, our cross-amyloid-inhibitor-design approach may be applicable to other aggregation-prone polypeptides or proteins.
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Biomimetic synthesis of the IDO inhibitors exiguamine A and B
04.08.2008
Nature Chemical Biology,
2008,
47,
doi:10.1038/nchembio.107
published on 01.08.2008
Nature Chemical Biology, online article
Nature Chemical Biology, online article
Biomimetic synthesis is an attempt to assemble natural products along biosynthetic lines without recourse to the full enzymatic machinery of nature. We exemplify this with a total synthesis of exiguamine A and the newly isolated natural product exiguamine B. The most noteworthy feature of this work is an oxidative endgame drawing from the complex chemistry of catecholamines, which allows for ready access to a new class of nanomolar indoleamine-2,3-
dioxygenase inhibitors.
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Sequence-Specific Conformational Flexibility of SNARE Transmembrane Helices Probed by Hydrogen/Deuterium Exchange
01.08.2008
Biophysical Journal,
2008,
95 , 3,
1326 - 35
published on 01.08.2008
Biophysical Journal, online article
Biophysical Journal, online article
SNARE proteins mediate fusion of intracellular eukaryotic membranes and their -helical transmembrane domains are known to contribute to lipid bilayer mixing. Synthetic transmembrane domain peptides were previously shown to mimic the function of SNARE proteins in that they trigger liposome fusion in a sequence-specific fashion. Here, we performed a detailed investigation of the conformational dynamics of the transmembrane helices of the presynaptic SNAREs synaptobrevin II and syntaxin 1a. To this end, we recorded deuterium/hydrogen-exchange kinetics in isotropic solution as well as in the membrane-embedded state. In solution, the exchange kinetics of each peptide can be described by three different classes of amide deuteriums that exchange with different rate constants. These are likely to originate from exchange at different domains of the helices. Interestingly, the rate constants of each class vary with the TMD sequence. Thus, the exchange rate is position-specific and sequence-specific. Further, the rate constants correlate with the previously determined membrane fusogenicities. In membranes, exchange is retarded and a significant proportion of amide hydrogens are protected from exchange. We conclude that the conformational dynamics of SNARE TMD helices is mechanistically linked to their ability to drive lipid mixing.
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Synthesis and properties of DNA containing a spore photoproduct analog
30.07.2008
The spore photoproduct is a unique photolesion, formed in spores
upon irradiation with UV light; to investigate the properties of
spore photoproduct containing DNA we have synthesized 5S and
5R lesion analogs and incorporated them into DNA.
Fpg (MutM) recognizes bulky N7-substituted-FapydG lesion using a novel and unproductive binding mode
21.07.2008
Chemistry & Biology,
2008,
15 (7),
706-17
published on 21.07.2008
Chemistry & Biology, online article
Chemistry & Biology, online article
Fpg (MutM) is a bacterial base excision repair enzyme that removes the mutagenic and/or replication-block lesions 8-oxoguanine (8-oxodG) and imidazole-ring opened purines (Fapy-derivatives) from DNA. This work shows that Fpg and its eukaryote homologue Ogg1 recognize with high affinity FapydG and bulky N7-benzyl-FapydG (Bz-FapydG). The comparative crystal structure analysis of stable complexes between Fpg and DNA duplex containing either carbocyclic cFapydG or Bz-cFapydG nucleoside provides the molecular bases of the ability of Fpg to bind both lesions with the same affinity. Both lesions are stabilized in an extrahelical anti glycosyl configuration inside the substrate binding pocket of the enzyme. To solve the steric hindrance of the benzyl group, Fpg selects the adequate rotamer of the Bz-cFapydG formamido group, allowing the expelling of the bulky group outside the binding pocket. Contrary to the binding mode of cFapydG, the particular recognition of Bz-cFapydG leads the enzyme in an unproductive complex. This work provides new structural and/or functional insights into Fpg substrate specificity and catalysis and has significant biological implications concerning the repair of bulky-Fapy-DNA adducts in vivo.
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Synthesis of a Stabilized Version of the Imidazolone DNA Lesion
28.05.2008
Imidazolone (dIz) is an abundant, highly mutagenic, and rather
unstable DNA lesion that can cause dG!dC transversion mutations.
dIz is generated in DNA by a variety of oxidative processes
such as type I photooxidation. Herein we report the synthesis of a
carbocyclic nucleoside analogue of dIz and of DNA containing
this stabilized lesion analogue. The carbocyclic modification protects
this lesion analogue from anomerization. As the repair of
the lesion analogue by DNA glycosylases is not possible, this analogue should allow cocrystallization studies together with wildtype repair enzymes. Characterization of the lesion analogue was performed by using spectroscopic methods and enzymatic digestion experiments of the oligonucleotides.
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Ubiquitin docking at the proteasome through a novel pleckstrin-homology domain interaction
22.05.2008
Targeted protein degradation is largely performed by the ubiquitin–proteasome pathway, in which substrate proteins are
marked by covalently attached ubiquitin chains that mediate
recognition by the proteasome. It is currently unclear how the
proteasome recognizes its substrates, as the only established ubiquitin receptor intrinsic to the proteasome is Rpn10/S5a (ref. 1), which is not essential for ubiquitin-mediated protein degradation in budding yeast2. In the accompanying manuscript we report that Rpn13 (refs 3–7), a component of the nine-subunit proteasome base, functions as a ubiquitin receptor8, complementing its known role in docking de-ubiquitinating enzyme Uch37/UCHL5 (refs 4–6) to the proteasome. Here we merge crystallography and NMRdata to describe the ubiquitin-binding mechanism of Rpn13. We determine the structure of Rpn13 alone and complexed with ubiquitin. The co-complex reveals a novel ubiquitin-binding mode in which loops rather than secondary structural elements are used to capture ubiquitin. Further support for the role of Rpn13 as a proteasomal ubiquitin receptor is demonstrated by its ability to bind ubiquitin and proteasome subunit Rpn2/S1 simultaneously. Finally, we provide a model structure of Rpn13 complexed to diubiquitin, which provides insights into how Rpn13 as a ubiquitin receptor is coupled to substrate deubiquitination by Uch37.
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News articles:
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Docking of tryptophan analogs to trytophanyl-tRNA synthetase: implications for non-canonical amino acid incorporations
22.05.2008
Biol.Chem,
2008,
378,
1173-82
published on 22.05.2008
The Journal Of Biological Chemistry, online article
The Journal Of Biological Chemistry, online article
Non-canonical amino acids (NAA), as building blocks for peptides and proteins during ribosomal translation, represent
a nearly infinite supply of novel functions. The specific selection, activation and tRNA-charging of amino acids by aminoacyl-tRNA synthetases (AARS) in the aminoacylation reaction are essential steps. In most cases, aminoacylation of NAA is a good indication that the related amino acid will participate in ribosomal translation as well. However, testing the translational capacity of amino acid analogs has technical limitations. Therefore, a rapid
and reliable in silico test for NAA recognition by AARS would be advantageous in experimental design. We chose tryptophanyl-tRNA synthetase from Escherichia coli as a model system for docking studies with various tryptophan analogs using the FlexX-Pharm strategy. We were able to calculate relative binding energies for Trp analogs in TrpRS that correlate well with their translational activities in E. coli. In particular, FlexX-Pharm predicted the binding sites of fluoro-, amino-, hydroxyl- and aza-containing Trp analogs within 1.5 A°
of Trp in the homology model of E. coli TrpRS. Therefore, the use of ligand docking prior to NAA incorporation experiments might provide a straightforward means for determining NAA that can be efficiently incorporated into a protein.
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A high-throughput assay based on fluorescence polarization for inhibitors of the polo-box domain of polo-like kinase
19.05.2008
Analytical Biochemistry,
2008,
doi:10.1016/j.ab.2008.08.014,
published on 19.05.2008
Analytical Biochemistry, online article
Analytical Biochemistry, online article
The serine/threonine kinase polo-like kinase 1 (Plk1) is critically involved in multiple mitotic processes and has been established as an adverse prognostic marker for tumor patients. Plk1 localizes to its substrates and its intracellular anchoring sites via its polo-box domain (PBD), which is unique to the family of polo-like kinases. Therefore, inhibition of the Plk1 PBD has been suggested as an approach to the inhibition of Plk1 that circumvents specificity problems associated with the inhibition of the conserved adenosine triphosphate (ATP) binding pocket. Here we report on the development of a high-throughput assay based on fluorescence polarization that allows the discovery of small-molecule inhibitors of the Plk1 PBD. The assay is based on binding of the Plk1 PBD to a phosphothreonine-containing peptide comprising its optimal binding motif with a Kd of 26 ± 2 nM. It is stable with regard to dimethyl sulfoxide (DMSO) and time, and it has a Z′ value of 0.73 ± 0.06 in a 384-well format.
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Inhibition of Polo-like Kinase 1 by Blocking Polo-Box Domain-Dependent Protein-Protein Interactions
16.05.2008
The serine/threonine kinase Polo-like kinase 1 (Plk1) is overexpressed in many types of human cancers, and has been implicated as an adverse prognostic marker for cancer patients. Plk1 localizes to its intracellular anchoring sites via its polo-box domain
(PBD). Here we show that Plk1 can be inhibited by small molecules which interfere with its intracellular localization by inhibiting the function of the PBD. We report the natural product thymoquinone and,
especially, the synthetic thymoquinone derivative Poloxin as inhibitors of the Plk1 PBD. Both compounds inhibit the function of the Plk1 PBD in vitro, and cause Plk1 mislocalization, chromosome congression
defects, mitotic arrest, and apoptosis in HeLa cells. Our data validate the Plk1 PBD as an anticancer target and provide a rationale for developing thymoquinone derivatives as anticancer drugs.
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Signal Transducers and Activators of Transcription as Targets for Small Organic Molecules
22.04.2008
Signal transducers and activators of transcription (STATs) are a
family of transcription factors that are of central importance for
cellular signaling and have therefore emerged as attractive
target proteins for cell-permeable small molecules. This review
outlines the basic concept of STAT signaling, the relevance of individual members of the STAT family for cellular signaling and
human disease, and generally applicable approaches taken to
the identification of small-molecule inhibitors of STATs.
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Temperature and pressure dependence of protein stability: The engineered fluorescein-binding lipocalin FluA shows an elliptic phase diagram
15.04.2008
We have measured the equilibrium constant for the denaturation
transition of the engineered fluorescein-binding lipocalin FluA as a function of pressure and temperature, taking advantage of the fact that the ligand’s fluorescence is almost fully quenched when complexed with the folded protein, but reversibly reappears on denaturation. From the equilibrium constant as a function of pressure and temperature all of the involved thermodynamic parameters of protein folding, in particular the changes in entropy and volume, compressibility, thermal expansion, and specific heat, were deduced in a global fitting procedure. Assuming that these parameters are independent of temperature and pressure, we can demonstrate from the ratio of Δβ, Δα², ΔCp that the phase diagram of protein folding assumes an elliptic shape. urthermore, we can show that the thermodynamic condition for such an elliptic phase diagram is related to the degree of correlation between the fluctuations of the changes in volume and enthalpy at the phase boundary. For the protein investigated this correlation is low, as generally expected for highly degenerate systems. Our study suggests that the elliptic phase diagram
is a consequence of the inherent conformational disorder of
proteins and that it may be viewed as the thermodynamic manifestation of the high degeneracy of conformational energies that is characteristic for this class of macromolecules.
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A plant pathogen virulence factor inhibits the eukaryotic proteasome by a novel mechanism
10.04.2008
Pathogenic bacteria often use effector molecules to increase virulence.vIn most cases, the mode of action of effectors remains
unknown. Strains of Pseudomonas syringae pv. syringae (Pss)
secrete syringolin A (SylA), a product of a mixed non-ribosomal
peptide/polyketide synthetase, in planta1. Here we identify SylA as
a virulence factor because a SylA-negative mutant in Pss strain B728a obtained by gene disruption was markedly less virulent
on its host, Phaseolus vulgaris (bean). We show that SylA irreversibly inhibits all three catalytic activities of eukaryotic proteasomes, thus adding proteasome inhibition to the repertoire of modes of action of virulence factors. The crystal structure of the
yeast proteasome in complex with SylA revealed a novel mechanism of covalent binding to the catalytic subunits. Thus, SylA
defines a new class of proteasome inhibitors that includes glidobactin A (GlbA), a structurally related compound from an unknown species of the order Burkholderiales2, for which we
demonstrate a similar proteasome inhibition mechanism. As proteasome inhibitors are a promising class of anti-tumour agents, the discovery of a novel family of inhibitory natural products,
which we refer to as syrbactins, may also have implications for
the development of anti-cancer drugs3. Homologues of SylA and
GlbA synthetase genes are found in some other pathogenic bacteria, including the human pathogen Burkholderia pseudomallei, the causative agent of melioidosis4. It is thus possible that these bacteria are capable of producing proteasome inhibitors of the syrbactin class.
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beta-Lactones as Privileged Structures for the Active-Site Labeling of Versatile Bacterial Enzyme Classes
09.04.2008
Angewandte Chemie,
2008,
47,
DOI: 10.1002/ anie.200705768
published on 09.04.2008
Angewandte Chemie International Edition, online article
Angewandte Chemie International Edition, online article
Evolution of multiresistant bacterial strains has meant that infectious diseases once again pose a major threat to public health. Since many antibiotics still target only a limited set of cellular functions, it is a desirable goal to expand the number and breadth of therapeutic targets as well as to gain a deeper understanding of the molecular mechanisms responsible for pathogenesis.To approach this goal, a chemical proteomic strategy (activity-based protein profiling, ABPP), developed by Evans and Cravatt, that uses active-site-directed probes was directly applied to bacterial proteomes. ABPP probes consist of at least two general elements: 1) a reactive group for binding and covalently modifying the active site of a certain enzyme class, and 2) a reporter tag for the detection,
enrichment, and identification of probe-labeled proteins.
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Efficient N-Terminal Glycoconjugation of Proteins by the N-End Rule
02.04.2008
The importance of protein N terminus sequence composition
for cell physiology was recognized more than two decades
ago. However, its relevance for chemical protein engineering
through an expanded genetic code was demonstrated only
very recently. Nature changes the chemistry of the N terminus
by posttranslational modifications (PTMs) such as longchain
alkylation, acetylation, myristoylation, glycosylation,
etc. This, in turn, influences the lifetimes and general metabolic
fates of tagged proteins in different ways according to
the N-end rules. Although Met is the first amino acid in a
newly synthesized protein, it is usually enzymatically removed
from the mature protein when the second position is occupied
by a non-bulky residue (for example, Ala, Cys, Gly). On the
other hand, bulky amino acids—such as Lys, Arg, Leu, Phe, and
Ile—in this position protect the N-terminal Met from being
processed. The extension of these rules to noncanonical
amino acids occupying the protein N terminus should enable
the in vivo generation of stable artificial N-terminal handles.
Their subsequent chemical derivatization might generate new
specific functions, especially if carbohydrates are attached.
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DIRK TRAUNER: HE IS BACK!
03.03.2008
2008,
published on 03.03.2008
Trauner Berkeley Webpage
Trauner Berkeley Webpage
2008 is great! We are very happy that Dirk Trauner will join CIPSM and the Department of Chemistry and Biochemistry of the LMU in August 08 as a newly established CIPSM full professor. Dirk's research centers on the total synthesis of complex natural products and rationally designed molecular probes and their application to biological problems, especially in neuroscience. We are looking forward to fruitful collaborations and amazing science. Dirk will rock the Munich scene. Watch out!
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From left to right: Herbert Mayr (Head of the Department), Dirk Trauner and Thomas Carell (Speaker of CIPSM).
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Synthetic Biology of Proteins: Tuning GFPs Folding and Stability with Fluoroproline
27.02.2008
Proline residues affect protein folding and stability via cis/trans isomerization of peptide bonds and by the Cc-exo or -endo puckering of their pyrrolidine rings. Peptide bond conformation as well as puckering propensity can be manipulated by proper choice of ring substituents, e.g. Cc-fluorination. Synthetic chemistry has routinely exploited ringsubstituted proline analogs in order to change, modulate or control folding and stability of peptides.
Methodology/Principal Findings:
n order to transmit this synthetic strategy to complex proteins, the ten proline residues of enhanced green fluorescent protein (EGFP) were globally replaced by (4R)- and (4S)-fluoroprolines (FPro). By this approach, we expected to affect the cis/trans peptidyl-proline bond isomerization and pyrrolidine ring puckering, which are responsible for the slow folding of this protein. Expression of both protein variants occurred at levels comparable to the parent protein, but the (4R)-FPro-EGFP resulted in irreversibly unfolded inclusion bodies, whereas the (4S)-FPro-EGFP led to a soluble fluorescent protein. Upon thermal denaturation, refolding of this variant occurs at significantly higher rates than the parent EGFP. Comparative inspection of the X-ray structures of EGFP and (4S)-FPro-EGFP allowed to correlate the significantly improved refolding with the Cc-endo puckering of the pyrrolidine rings, which is favored by 4S-fluorination, and to lesser extents with the cis/trans isomerization of the prolines.
Conclusions/Significance:
We discovered that the folding rates and stability of GFP are affected to a lesser extent by cis/trans isomerization of the proline bonds than by the puckering of pyrrolidine rings. In the Cc-endo conformation the fluorine atoms are positioned in the structural context of the GFP such that a network of favorable local interactions is established. From these results the combined use of synthetic amino acids along with detailed structural knowledge and existing protein engineering methods can be envisioned as a promising strategy for the design of complex tailor-made proteins and even cellular structures of superior properties compared to the native forms.
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Discovery of Chromone-Based Inhibitors of the Transcription Factor STAT5
05.02.2008
Molecular signals originating at the cell surface are conveyed
by a complex system of interconnected signaling pathways to
the nucleus. They converge at transcription factors, which in
turn regulate the transcription of sets of genes which ultimately
determine the cellular phenotype. Whereas enzymes involved
in signaling pathways, that is, intracellular kinases and
phosphatases and receptor tyrosine kinases, have been recognized
and exploited as intervention points for modulating cellular
properties with small organic molecules, transcription
factors are often considered “nondruggable” because of their
lack of enzymatic activities. However, as many transcription
factors require interactions with themselves or other proteins,
cell-permeable inhibitors of protein–protein interactions could
provide an approach towards the inhibition of this important
class of proteins, and would thereby allow for the analysis of
transcription factor functions and for therapeutic intervention
of diseased states. Initially regarded as unfeasible, a growing
body of evidence indicates that the inhibition of protein–protein
interactions can be potently and selectively achieved by
drug-like molecules, some of which are even undergoing
clinical trials.
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Synthesis of DNA Dumbbell Based Inhibitors for the Human DNA Methyltransferase Dnmt1
18.01.2008
DNA methyltransferases convert deoxycytidine (dC) nucleobases
in DNA into 5-methyldeoxycytidines (dCMe) using the cofactor S-adenosylmethionine (SAM) as the methyl group donor.Methylation of the canonical dC base, particularly in gene promoter regions, induces complex processes, which finally lead to the silencing of the corresponding gene. This epigenetic gene silencing is of paramount importance for cellular differentiation.Altered methylation patterns and
corresponding changes in gene expression are found in practically all tumor cells. The major DNA methyltransferase Dnmt1 is a 183-kDa-large protein that preferentially methylates dC bases in hemimethylated d(CpG) sequences after DNA replication.
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A high-throughput assay for signal transducer and activator of transcription 5b based on fluorescence polarization
18.01.2008
Analytical Biochemistry,
2008,
375,
249-54
published on 18.01.2008
Analytical Biochemistry, online article
Analytical Biochemistry, online article
Signal transducer and activator of transcription 5b (STAT5b) is constitutively activated in many human tumors. Activity of STAT5b
requires binding of its Src homology 2 (SH2) domain to certain phosphotyrosine-containing sequences. We have developed a highthroughput assay based on fluorescence polarization that allows screening of chemical libraries for compounds that inhibit STAT5b
by interfering with the function of its SH2 domain. The assay, which is based on binding between a fluorescein-labeled phosphotyrosine
peptide derived from the erythropoietin receptor to the STAT5b SH2 domain, is stable with regard to dimethyl sulfoxide concentration
and time and has a Z0 value of 0.66 ± 0.11 in a 384-well format.
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Dissecting the Differences between the a and b Anomers of the Oxidative DNA Lesion FaPydG
14.01.2008
The oxidative DNA lesion, FaPydG rapidly anomerizes to form a
mixture of the a and b anomer. To investigate the mutagenic potential of both forms, we prepared stabilized bioisosteric analogues of both configurational isomers and incorporated them
into oligonucleotides. These were subsequently used for thermodynamic melting-point studies and for primerextension
experiments. While the b compound, in agreement with earlier
data, prefers cytidine as the pairing partner, the a compound is not able form a stable base pair with any natural base. In primer-extension studies with the high-fidelity polymerase Bst
Pol I, the polymerase was able to read through the lesion. The b compound showed no strong mutagenic potential. The a compound, in contrast, strongly destabilized DNA duplexes and also blocked all of the tested DNA polymerases, including two low-fidelity polymerases of the Y-family.
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The carbohydrate recognition domain of Langerin reveals high structural similarity with the one of DC-SIGN but an additional, calcium-independent sugar-binding site
03.12.2007
Langerin is a type II transmembrane oligosaccharide receptor on Langerhans cells (LCs), a prominent subclass of dendritic cells (DCs) that mediate immune responses in epithelia and play a role in HIV degradation. Its extracellular moiety comprises a neck region with several heptad repeats and an exposed carboxy-terminal calcium-type carbohydrate-recognition domain (CRD). The CRD of human Langerin, which was expressed as a soluble protein in the periplasm of E. coli, was crystallized both alone and in the presence of two sugars, followed by X-ray analyses to
resolutions of 2.5 °A for apo-Langerin and to 1.6 °A and 2.1 °A for the complexes with mannose and maltose, respectively. The fold of the Langerin CRD (dubbed LangA) resembles that of other typical C-type lectins such as DC-SIGN. However, especially in the long loop region (LLR), which is responsible for carbohydrate-binding, two additional secondary structure elements are present: a 310 helix and a small b-sheet arising from the
extended b-strand 2, which enters into a hairpin and a new strand b2´. Unexpectedly, the crystal structures in the presence of maltose and mannose reveal two sugar-binding sites. One is calcium-dependent and structurally conserved in the C-type lectin family whereas the second one represents a novel, calcium-independent type. Based on these data, a model for the binding of mannan, a component of many endogenous as well as viral
glycoproteins, is proposed and the differences in binding behavior between Langerin and DC-SIGN with respect to the Lewis X carbohydrate antigen and its derivatives can be explained. Therefore, the crystal structure of LangA should be helpful for the development of new marker reagents
selective for LCs and also of therapeutic compounds that may enhance the inhibitory role of Langerin towards HIV infection.
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Bayer Schering Pharma and CIPSM sign a strategic partnership
13.02.2008
published on 13.02.2007
www.bayerscheringpharma.de
www.bayerscheringpharma.de
Bayer Schering Pharma (BSP) and CIPSM sign a strategic partnership. The aim of both partners is to initiate a scientific exchange and to carry out joint projects in the field of protein chemistry. With this cooperation the partners wish to simplify and essentially accelerate the transfer of fundamental perceptions into applications, in order to score a leading position in this international highly competitive research topics.
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Exzellenzcluster und Bayer Schering Pharma schließen strategische Kooperation
München, 13. Februar 2008 – Das Münchner Exzellenzcluster Center for Integrated Protein Science Munich (CIPSM) und Bayer Schering Pharma (BSP) haben eine strategische Partnerschaft vereinbart. Ziel der Partnerschaft ist, auf dem Gebiet der Proteinchemie einen intensiven wissenschaftlichen Austausch zu initiieren und gemeinsame Projekte durchzuführen. Die Partner möchten so die Überführung von Grundlagenerkenntnissen in die Anwendung vereinfachen und wesentlich beschleunigen, um in international umkämpften Forschungsthemen eine führende Position zu erzielen.
Im Rahmen der Kollaboration zwischen dem an der LMU München angesiedelten Cluster und dem Pharmaunternehmen sollen die Kompetenzen beider Organisationen zusammengeführt und genutzt werden. „Wir sind davon überzeugt, dass sich durch den intensiven Dialog nicht nur neue Impulse für die Arzneimittelentwicklung ergeben, sondern im Gegenzug auch wertvolle Erkenntnisse für die Grundlagenforschung gewonnen werden”, sagt Cluster-Sprecher Professor Thomas Carell. „Partnerschaften wie diese sind wichtig, um eine Plattform für den Wissens- und Know-how-Austausch zu schaffen, um so den Wissenschafts- und Wirtschaftsstandort Deutschland nachhaltig zu stärken.”
Neben der Etablierung von Dialogplattformen steht die Initiierung gemeinsamer Forschungsprojekte im Vordergrund. So werden in einem ersten Projekt, an dem Wissenschaftler beider Organisationen in Wuppertal und München beteiligt sind, neue Ansätze zur Proteinmodifikation und -stabilisierung untersucht. Diese Arbeiten bilden wichtige Grundlagen für die Entwicklung therapeutischer Proteine.
Ansprechpartner:
Dr. Oliver Baron
Geschäftsführer / Scientific Manager CIPSM
Tel: +49 (0)89 / 2180 – 77661 oder – 77653
E-Mail : oliver.baron@cipsm.de
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CIPSM ist Ausgewählter Ort im Land der Ideen
25.11.2008
25. November 2008,
published on
Deutschland Land der Ideen
Deutschland Land der Ideen
YEAH! CIPSM ist „Ausgewählter Ort im Land der Ideen“. Damit ist CIPSM Teil der Veranstaltungsreihe „365 Orte im Land der Ideen“, die gemeinsam von der Standortinitiative „Deutschland – Land der Ideen“ und der Deutschen Bank durchgeführt wird.
Als „Ausgewählter Ort“ wird CIPSM unter der Schirmherrschaft von Bundespräsident Horst Köhler im Jahr 2009 Deutschland als das „Land der Ideen“ repräsentieren und die Innovationsfreude unseres Landes erlebbar machen.
Aus Anlass der Preisverleihung veranstalten wir am 4. Mai 2009 im Deutschen Museum eine Party mit Vorträgen zum Thema "Proteinforschung für wirksamere Medikamente" für alle die mitfeiern möchten.
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