title: Cyclic heptapeptide microcystin biosynthesis requires the glutamate racemase gene.
abstract: It was demonstrated previously that the operon consisting of the non-ribosomal peptide synthetase (NRPS) gene coupled with the polyketide synthase (PKS) gene involved in cyclic heptapeptide microcystin synthesis includes two different D-amino acid synthetase genes, an epimerization domain at the 3' end of module 2, and the racemase gene mcyF. To determine the role of mcyF in microcystin synthesis, gene-disruption and complementation analyses were carried out. Insertional mutagenesis in the mcyF gene, generated by homologous recombination, abolished only microcystin synthesis, but did not influence cell growth. Furthermore, McyF supported D-Glu-independent growth of a strain of Escherichia coli defective in D-Glu synthesis. It is concluded that mcyF is the glutamic acid racemase gene involved in the synthesis of D-Glu residues in the microcystin molecule. This is the first report of the racemase in prokaryotic NRPS.
authors.affiliation: The United Graduate School, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan3.|Laboratory of Molecular Genetics, School of Agriculture1, and Gene Research Center2, Ibaraki University, Ami, Ibaraki 300-0393, Japan.
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Nishizawa
authors.affiliation: Laboratory of Molecular Genetics, School of Agriculture1, and Gene Research Center2, Ibaraki University, Ami, Ibaraki 300-0393, Japan.
authors.forename: Munehiko
authors.initials: M
authors.lastname: Asayama
authors.affiliation: Laboratory of Molecular Genetics, School of Agriculture1, and Gene Research Center2, Ibaraki University, Ami, Ibaraki 300-0393, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shirai
mesh_terms: D000591:Amino Acid Isomerases / Q000235:genetics* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D018698:Glutamic Acid / Q000096:biosynthesis; D052998:Microcystins; D016254:Mutagenesis, Insertional; D009876:Operon; D010453:Peptide Synthases / Q000235:genetics* / Q000378:metabolism; D010456:Peptides, Cyclic / Q000378:metabolism*; D010802:Phylogeny; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D052998:Microcystins; D010456:Peptides, Cyclic; D011994:Recombinant Proteins; D018698:Glutamic Acid; C078588:microcystin; D000591:Amino Acid Isomerases; C062292:glutamate racemase; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase