title: The hidden steps of domain skipping: macrolactone ring size determination in the pikromycin modular polyketide synthase.
abstract: The pikromycin (Pik) polyketide synthase (PKS) from Streptomyces venezuelae comprises four multifunctional polypeptides (PikAI, PikAII, PikAIII, and PikAIV). This PKS can generate 12- and 14-membered ring macrolactones (10-deoxymethynolide and narbonolide, respectively) through the activity of its terminal modules (PikAIII and PikAIV). We performed a series of experiments involving the functional replacement of PikAIV in mutant strains with homodimeric and heterodimeric PikAIV modules to investigate the details of macrolactone ring size determination. The results suggest a new and surprising mechanism by which the penultimate hexaketide chain elongation intermediate is transferred from PikAIII ACP5 to PikAIV ACP6 before release by the terminal thioesterase domain. Elucidation of this chain transfer mechanism provides important new details about alternative macrolactone ring size formation in modular PKSs and contributes to the potential for rational design of structural diversity by combinatorial biosynthesis.
authors.affiliation: Department of Microbiology and Biotechnology Institute, University of Minnesota, Mayo Mail Code 196, 420 Delaware Street S.E., Minneapolis, MN 55455, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Beck
authors.forename: Yeo Joon
authors.initials: YJ
authors.lastname: Yoon
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Reynolds
authors.forename: David H
authors.initials: DH
authors.lastname: Sherman
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D020134:Catalytic Domain; D019281:Dimerization; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D007783:Lactones / Q000138:chemical synthesis / Q000378:metabolism*; D018942:Macrolides / Q000138:chemical synthesis* / Q000378:metabolism; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010957:Plasmids / Q000096:biosynthesis / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D007783:Lactones; D018942:Macrolides; D009097:Multienzyme Complexes; C079477:10-deoxymethynolide; C003145:picromycin