title: Hedycaryol synthase in complex with nerolidol reveals terpene cyclase mechanism.
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.
authors.affiliation: Center for Integrated Protein Science at the Department of Chemistry, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching (Germany).
authors.forename: Philipp
authors.initials: P
authors.lastname: Baer
authors.forename: Patrick
authors.initials: P
authors.lastname: Rabe
authors.forename: Christian A
authors.initials: CA
authors.lastname: Citron
authors.forename: Carina C
authors.initials: CC
authors.lastname: de Oliveira Mann
authors.forename: Norman
authors.initials: N
authors.lastname: Kaufmann
authors.forename: Michael
authors.initials: M
authors.lastname: Groll
authors.forename: Jeroen S
authors.initials: JS
authors.lastname: Dickschat
mesh_terms: D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D008025:Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D016296:Mutagenesis; D009154:Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012717:Sesquiterpenes / Q000378:metabolism*; D013306:Streptomycetaceae / Q000201:enzymology; D013729:Terpenes / Q000378:metabolism*
chemical_list: D012717:Sesquiterpenes; D013729:Terpenes; D008025:Ligases; C037055:nerolidol
keywords: X-ray diffraction; biosynthesis; crystal structures; enzyme mechanisms; hedycaryol synthases; terpenes