title: Structural rearrangements of a polyketide synthase module during its catalytic cycle.
abstract: 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.
authors: 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Chemical Biology Graduate Program, University of Michigan, Ann Arbor, Michigan 48109, USA [3].
authors: Jonathan R
authors: JR
authors: Whicher
authors: 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2].
authors: Somnath
authors: S
authors: Dutta
authors: 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Douglas A
authors: DA
authors: Hansen
authors: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Wendi A
authors: WA
authors: Hale
authors: Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Joseph A
authors: JA
authors: Chemler
authors: Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Annie M
authors: AM
authors: Dosey
authors: Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Alison R H
authors: AR
authors: Narayan
authors: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Kristina
authors: K
authors: Håkansson
authors: 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Medicinal Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA [3] Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA [4] Department of Microbiology & Immunology, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: David H
authors: DH
authors: Sherman
authors: 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Janet L
authors: JL
authors: Smith
authors: 1] Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, USA [2] Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Georgios
authors: G
authors: Skiniotis
mesh_terms: D000213:Acyl Carrier Protein / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D000217:Acyltransferases / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D055162:Biocatalysis; D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D018942:Macrolides / Q000378:metabolism; D008958:Models, Molecular; D048630:Polyketide Synthases / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D013302:Streptomyces / Q000201:enzymology*
chemical_list: D000213:Acyl Carrier Protein; D001426:Bacterial Proteins; D018942:Macrolides; D048630:Polyketide Synthases; D000429:Alcohol Oxidoreductases; C087192:polyketide synthase ketoreductase; D000217:Acyltransferases; C003145:picromycin