Structural rearrangements of a polyketide synthase module during its catalytic cycle

The polyketide synthase (PKS) mega-enzyme assembly line uses a modular architecture to synthesize diverse and bioactive natural products that often constitute the core structures or complete chemical entities for many clinically approved therapeutic agents. The architecture of a full-length PKS modu...

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Bibliographic Details
Published in:Nature (London) 2014-06, Vol.510 (7506), p.560-564
Main Authors: Whicher, Jonathan R, Dutta, Somnath, Hansen, Douglas A, Hale, Wendi A, Chemler, Joseph A, Dosey, Annie M, Narayan, Alison R H, Håkansson, Kristina, Sherman, David H, Smith, Janet L, Skiniotis, Georgios
Format: Article
Language:English
Subjects:
Acyl Carrier Protein - chemistry
Acyl Carrier Protein - metabolism
Acyl Carrier Protein - ultrastructure
Acyltransferases - chemistry
Acyltransferases - metabolism
Acyltransferases - ultrastructure
Alcohol Oxidoreductases - chemistry
Alcohol Oxidoreductases - metabolism
Alcohol Oxidoreductases - ultrastructure
Bacterial Proteins - chemistry
Bacterial Proteins - metabolism
Bacterial Proteins - ultrastructure
Biocatalysis
Biosynthesis
Catalytic Domain
Chromatography
Cryoelectron Microscopy
Crystal structure
Fourier transforms
Health aspects
Macrolides - metabolism
Models, Molecular
Observations
Polyketide Synthases - chemistry
Polyketide Synthases - metabolism
Polyketide Synthases - ultrastructure
Polyketides
Protein Structure, Tertiary
Protein-protein interactions
Proteins
Streptomyces
Streptomyces - enzymology
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Summary:The polyketide synthase (PKS) mega-enzyme assembly line uses a modular architecture to synthesize diverse and bioactive natural products that often constitute the core structures or complete chemical entities for many clinically approved therapeutic agents. The architecture of a full-length PKS module from the pikromycin pathway of Streptomyces venezuelae creates a reaction chamber for the intramodule acyl carrier protein (ACP) domain that carries building blocks and intermediates between acyltransferase, ketosynthase and ketoreductase active sites (see accompanying paper). Here we determine electron cryo-microscopy structures of a full-length pikromycin PKS module in three key biochemical states of its catalytic cycle. Each biochemical state was confirmed by bottom-up liquid chromatography/Fourier transform ion cyclotron resonance mass spectrometry. The ACP domain is differentially and precisely positioned after polyketide chain substrate loading on the active site of the ketosynthase, after extension to the β-keto intermediate, and after β-hydroxy product generation. The structures reveal the ACP dynamics for sequential interactions with catalytic domains within the reaction chamber, and for transferring the elongated and processed polyketide substrate to the next module in the PKS pathway. During the enzymatic cycle the ketoreductase domain undergoes dramatic conformational rearrangements that enable optimal positioning for reductive processing of the ACP-bound polyketide chain elongation intermediate. These findings have crucial implications for the design of functional PKS modules, and for the engineering of pathways to generate pharmacologically relevant molecules.
ISSN:0028-0836
1476-4687
DOI:10.1038/nature13409