title: Type I polyketide synthase requiring a discrete acyltransferase for polyketide biosynthesis.
abstract: Type I polyketide synthases (PKSs) are multifunctional enzymes that are organized into modules, each of which minimally contains a beta-ketoacyl synthase, an acyltransferase (AT), and an acyl carrier protein. Here we report that the leinamycin (LNM) biosynthetic gene cluster from Streptomyces atroolivaceus S-140 consists of two PKS genes, lnmI and lnmJ, that encode six PKS modules, none of which contain the cognate AT domain. The only AT activity identified within the lnm gene cluster is a discrete AT protein encoded by lnmG. Inactivation of lnmG, lnmI, or lnmJ in vivo abolished LNM biosynthesis. Biochemical characterization of LnmG in vitro showed that it efficiently and specifically loaded malonyl CoA to all six PKS modules. These findings unveiled a previously unknown PKS architecture that is characterized by a discrete, iteratively acting AT protein that loads the extender units in trans to "AT-less" multifunctional type I PKS proteins for polyketide biosynthesis. This PKS structure provides opportunities for PKS engineering as exemplified by overexpressing lnmG to improve LNM production.
authors.affiliation: Division of Pharmaceutical Sciences, Department of Chemistry, University of Wisconsin, 777 Highland Avenue, Madison, WI 53705, USA.
authors.forename: Yi-Qiang
authors.initials: YQ
authors.lastname: Cheng
authors.forename: Gong-Li
authors.initials: GL
authors.lastname: Tang
authors.forename: Ben
authors.initials: B
authors.lastname: Shen
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D007769:Lactams; D018942:Macrolides; D008316:Malonyl Coenzyme A / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D010802:Phylogeny; D015202:Protein Engineering; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics; D013844:Thiazoles; D013871:Thiones
chemical_list: D000903:Antibiotics, Antineoplastic; D017931:DNA Primers; D007769:Lactams; D018942:Macrolides; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D013844:Thiazoles; D013871:Thiones; C059000:leinamycin; D008316:Malonyl Coenzyme A