Induced-Fit Mechanism in Class I Terpene Cyclases

Angewandte Chemie, 2014, DOI: 10.1002/anie.201403648, Volume 53, Issue 29, pages 7652–7656, published on 30.05.2014
Angewandte Chemie, online article
We present crystallographic and functional data of selina-4(15),7(11)-diene synthase (SdS) from Streptomyces pristinaespiralis in its open and closed (ligand-bound) conformation. We could identify an induced-fit mechanism by elucidating a rearrangement of the G1/2 helix-break motif upon substrate binding. This rearrangement highlights a novel effector triad comprising the pyrophosphate sensor Arg178, the linker Asp181, and the effector Gly182-O. This structural motif is strictly conserved in class I terpene cyclases from bacteria, fungi, and plants, including epi-isozizaene synthase (3KB9), aristolochene synthase (4KUX), bornyl diphosphate synthase (1N20), limonene synthase (2ONG), 5-epi-aristolochene synthase (5EAT), and taxa-4(5),11(12)-diene synthase (3P5R). An elaborate structure-based mutagenesis in combination with analysis of the distinct product spectra confirmed the mechanistic models of carbocation formation and stabilization in SdS.  

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