title: The barbamide biosynthetic gene cluster: a novel marine cyanobacterial system of mixed polyketide synthase (PKS)-non-ribosomal peptide synthetase (NRPS) origin involving an unusual trichloroleucyl starter unit.
abstract: Barbamide was extracted from the marine cyanobacterium Lyngbya majuscula strain 19L as a chlorinated lipopeptide for its potent molluscicidal activity. Precursor incorporation studies indicated that it is derived from acetate, L-phenylalanine, L-leucine and L-cysteine. The gene cluster responsible for biosynthesis of barbamide (bar) was cloned and characterized in this study. DNA sequence analysis of cosmid pLM49 revealed a cluster of 12 open reading frames (barA-barK) extending 26 kb including the expected polyketide synthase and non-ribosomal peptide synthetase modules and tailoring genes. The genetic architecture and domain organization of the bar cluster supports the assignment based on the apparent co-linearity of the systems. The activity assay of adenylation domains of barD (A(D)), barE (A(E)) and barG (A(G2) for module 2) in an amino acid-dependent ATP-pyrophosphate exchange experiment supports the conclusion that barbamide is synthesized from acetate, L-phenylalanine, L-cysteine and L-leucine with trichloroleucine as a direct precursor by a mixed polyketide synthase/non-ribosomal polypeptide synthetase. Assembly of barbamide includes unique biochemical mechanisms for chlorination, one-carbon truncation during chain elongation, E-double bond formation and thiazole ring formation.
authors.affiliation: Department of Microbiology and BioTechnology Institute, University of Minnesota, 1460 Mayo Memorial Building, MMC 196, 420 Delaware Street S.E., Minneapolis 55455, USA.
authors.forename: Zunxue
authors.initials: Z
authors.lastname: Chang
authors.forename: Patricia
authors.initials: P
authors.lastname: Flatt
authors.forename: William H
authors.initials: WH
authors.lastname: Gerwick
authors.forename: Viet-Anh
authors.initials: VA
authors.lastname: Nguyen
authors.forename: Christine L
authors.initials: CL
authors.lastname: Willis
authors.forename: David H
authors.initials: DH
authors.lastname: Sherman
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D023061:Gene Order; D005798:Genes, Bacterial / Q000235:genetics; D015698:Genomic Library; D007930:Leucine / Q000031:analogs & derivatives / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D005810:Multigene Family / Q000235:genetics*; D010453:Peptide Synthases / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013844:Thiazoles / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D009097:Multienzyme Complexes; D013844:Thiazoles; C100545:barbamide; D000255:Adenosine Triphosphate; D010453:Peptide Synthases; D007930:Leucine