title: Domain Organization and Active Site Architecture of a Polyketide Synthase C-methyltransferase.
abstract: Polyketide metabolites produced by modular type I polyketide synthases (PKS) acquire their chemical diversity through the variety of catalytic domains within modules of the pathway. Methyltransferases are among the least characterized of the catalytic domains common to PKS systems. We determined the domain boundaries and characterized the activity of a PKS C-methyltransferase (C-MT) from the curacin A biosynthetic pathway. The C-MT catalyzes S-adenosylmethionine-dependent methyl transfer to the α-position of β-ketoacyl substrates linked to acyl carrier protein (ACP) or a small-molecule analog but does not act on β-hydroxyacyl substrates or malonyl-ACP. Key catalytic residues conserved in both bacterial and fungal PKS C-MTs were identified in a 2 Å crystal structure and validated biochemically. Analysis of the structure and the sequences bordering the C-MT provides insight into the positioning of this domain within complete PKS modules.
authors.affiliation: Life Sciences Institute, University of Michigan , Ann Arbor, Michigan, United States.|Department of Biological Chemistry, University of Michigan , Ann Arbor, Michigan, United States.
authors.forename: Meredith A
authors.initials: MA
authors.lastname: Skiba
authors.affiliation: Life Sciences Institute, University of Michigan , Ann Arbor, Michigan, United States.|Department of Biological Chemistry, University of Michigan , Ann Arbor, Michigan, United States.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Sikkema
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota, United States.
authors.forename: William D
authors.initials: WD
authors.lastname: Fiers
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego , La Jolla, California, United States.|School of Pharmacy and Pharmaceutical Sciences, University of California San Diego , La Jolla, California, United States.
authors.forename: William H
authors.initials: WH
authors.lastname: Gerwick
authors.affiliation: Life Sciences Institute, University of Michigan , Ann Arbor, Michigan, United States.|Department of Medicinal Chemistry, University of Michigan , Ann Arbor, Michigan, United States.|Department of Chemistry, University of Michigan , Ann Arbor, Michigan, United States.|Department of Microbiology and Immunology, University of Michigan , Ann Arbor, Michigan, United States.
authors.forename: David H
authors.initials: DH
authors.lastname: Sherman
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota , Minneapolis, Minnesota, United States.
authors.forename: Courtney C
authors.initials: CC
authors.lastname: Aldrich
authors.affiliation: Life Sciences Institute, University of Michigan , Ann Arbor, Michigan, United States.|Department of Biological Chemistry, University of Michigan , Ann Arbor, Michigan, United States.
authors.forename: Janet L
authors.initials: JL
authors.lastname: Smith
mesh_terms: D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D003521:Cyclopropanes / Q000378:metabolism; D008780:Methyltransferases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D048630:Polyketide Synthases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D013844:Thiazoles / Q000378:metabolism
chemical_list: D003521:Cyclopropanes; D013844:Thiazoles; C095843:curacin A; D048630:Polyketide Synthases; D008780:Methyltransferases