title: Characterization of Streptomyces argillaceus genes encoding a polyketide synthase involved in the biosynthesis of the antitumor mithramycin.
abstract: Mithramycin (Mtm) is an aromatic polyketide which shows antibacterial and antitumor activity. From a chromosomal cosmid library of Streptomyces argillaceus, a Mtm producer, a clone (cosAR7) was isolated by homology to the actI/III region of S. coelicolor and the strDEM genes of S. griseus. From this clone, a 5.3-kb DNA region was sequenced and found to encode six open reading frames (designated as mtmQXPKST1), five of them transcribed in the same direction. The deduced products of five of these genes resembled components of type-II polyketide synthases. The mtm genes would code for an aromatase (mtmQ), a polypeptide of unknown function (mtmX), a beta-ketoacylsynthase (mtmP) and a related 'chain length factor' (mtmK), an acyl carrier protein (mtmS) and a beta-ketoreductase (mtmT1). The involvement of this gene cluster in Mtm biosynthesis was demonstrated by the Mtm non-producing phenotype of mutants generated in two independent insertional inactivation experiments.
authors.affiliation: Departamento de Biología Funcional, Instituto Universitario de Biotecnología de Asturias (I.U.B.A-C.S.I.C), Universidad de Oviedo, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Lombó
authors.forename: G
authors.initials: G
authors.lastname: Blanco
authors.forename: E
authors.initials: E
authors.lastname: Fernández
authors.forename: C
authors.initials: C
authors.lastname: Méndez
authors.forename: J A
authors.initials: JA
authors.lastname: Salas
mesh_terms: D000595:Amino Acid Sequence; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis*; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D005810:Multigene Family; D008926:Plicamycin / Q000096:biosynthesis*; D013302:Streptomyces / Q000235:genetics*
chemical_list: D000903:Antibiotics, Antineoplastic; D004269:DNA, Bacterial; D009097:Multienzyme Complexes; D008926:Plicamycin