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Structural basis for macrolactonization by the pikromycin thioesterase.

David L Akey·Jeffrey D Kittendorf·John W Giraldes·Robert A Fecik·David H Sherman·Janet L Smith
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Abstract

Polyketides are a class of biologically active microbial and plant-derived metabolites that possess a high degree of structural and functional diversity and include many human therapeutics, among them anti-infective and anti-cancer drugs, growth promoters and anti-parasitic agents. The macrolide antibiotics, characterized by a glycoside-linked macrolactone, constitute an important class of polyketides, including erythromycin and the natural ketolide anti-infective agent pikromycin. Here we describe new mechanistic details of macrolactone ring formation catalyzed by the pikromycin polyketide synthase thioesterase domain from Streptomyces venezuelae. A pentaketide phosphonate mimic of the final pikromycin linear chain-elongation intermediate was synthesized and shown to be an active site affinity label. The crystal structures of the affinity-labeled enzyme and of a 12-membered-ring macrolactone product complex suggest a mechanism for cyclization in which a hydrophilic barrier in the enzyme and structural restraints of the substrate induce a curled conformation to direct macrolactone ring formation.

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Binding SitesBiphenyl CompoundsCatalysisCrystallizationCyclizationEnzyme ActivationEnzyme InhibitorsMacrolidesModels, MolecularMolecular ConformationOrganophosphonatesProtein ConformationProtein Structure, TertiaryStereoisomerismStreptomycesStructure-Activity RelationshipThiolester HydrolasesX-Ray DiffractionJournal ArticleResearch Support, N.I.H., ExtramuralResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, Non-P.H.S.

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David L Akey, Jeffrey D Kittendorf, John W Giraldes, Robert A Fecik, David H Sherman, Janet L Smith. 2006-09-10. Structural basis for macrolactonization by the pikromycin thioesterase.. https://doi.org/10.1038/nchembio824

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