Hedycaryol synthase in complex with nerolidol reveals terpene cyclase mechanism.
Baer, P., Rabe, P., Citron, C.A., de Oliveira Mann, C.C., Kaufmann, N., Groll, M., Dickschat, J.S.(2014) Chembiochem 15: 213-216
- PubMed: 24399794 
- DOI: https://doi.org/10.1002/cbic.201300708
- Primary Citation of Related Structures:  
4MC0, 4MC3, 4MC8 - PubMed Abstract: 
The biosynthesis of terpenes is catalysed by class I and II terpene cyclases. Here we present structural data from a class I hedycaryol synthase in complex with nerolidol, serving as a surrogate for the reaction intermediate nerolidyl diphosphate. This prefolded ligand allows mapping of the active site and hence the identification of a key carbonyl oxygen of Val179, a highly conserved helix break (G1/2) and its corresponding helix dipole. Stabilising the carbocation at the substrate's C1 position, these elements act in concert to catalyse the 1,10 ring closure, thereby exclusively generating the anti-Markovnikov product. The delineation of a general mechanistic scaffold was confirmed by site-specific mutations. This work serves as a basis for understanding carbocation chemistry in enzymatic reactions and should contribute to future application of these enzymes in organic synthesis.
Organizational Affiliation: 
Center for Integrated Protein Science at the Department of Chemistry, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching (Germany).