title: Involvement of a chromomycin ABC transporter system in secretion of a deacetylated precursor during chromomycin biosynthesis.
abstract: Chromomycin A(3) is an antitumour antibiotic that acts by inhibiting transcription and replication of DNA. The producer micro-organism Streptomyces griseus subsp. griseus is highly resistant to chromomycin A(3) and to the structurally related compound mithramycin upon induction with chromomycin A(3). The biosynthetic gene cluster of chromomycin contains three genes involved in self-resistance to chromomycin in S. griseus: cmrA and cmrB encode a type I ATP-binding cassette (ABC) transporter, and cmrX encodes a UvrA-like protein of ABC excision nuclease systems. These genes are linked in the chromosome, together with a gene encoding a transcriptional repressor (cmmRII). Involvement of these genes in chromomycin resistance was determined through gene inactivation, and heterologous expression in Streptomyces albus. Inactivation of cmrX produced a chromomycin-sensitive low-producer strain, while inactivation of cmmRII generated a high-chromomycin-producer strain, which was resistant to chromomycin, and also to mithramycin. Expression of either cmrA and cmrB, or cmrX, in S. albus generated strains with low chromomycin resistance; it was therefore necessary to co-express the three genes to achieve high levels of resistance. However, the CmrAB ABC transporter conferred a high level of resistance to the biosynthesis intermediate 4A,4E-O-dideacetyl-chromomycin A(3). A model is proposed for the biosynthesis of, and self-resistance to, chromomycin A(3) in S. griseus subsp. griseus.
authors.affiliation: Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, Oviedo, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Menéndez
authors.affiliation: Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, Oviedo, Spain.
authors.forename: Alfredo F
authors.initials: AF
authors.lastname: Braña
authors.affiliation: Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, Oviedo, Spain.
authors.forename: José A
authors.initials: JA
authors.lastname: Salas
authors.affiliation: Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, Oviedo, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Méndez
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000107:Acetylation; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis* / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D014128:Chromomycin A3 / Q000096:biosynthesis* / Q000737:chemistry / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D008926:Plicamycin / Q000737:chemistry; D011498:Protein Precursors / Q000737:chemistry / Q000378:metabolism*; D013302:Streptomyces / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D018528:ATP-Binding Cassette Transporters; D000903:Antibiotics, Antineoplastic; D001426:Bacterial Proteins; D011498:Protein Precursors; D014128:Chromomycin A3; D008926:Plicamycin