The mithramycin gene cluster of Streptomyces argillaceus contains a positive regulatory gene and two repeated DNA sequences that are located at both ends of the cluster.
Sequencing of a 4.3-kb DNA region from the chromosome of Streptomyces argillaceus, a mithramycin producer, revealed the presence of two open reading frames (ORFs). The first one (orfA) codes for a protein that resembles several transport proteins. The second one (mtmR) codes for a protein similar to positive regulators involved in antibiotic biosynthesis (DnrI, SnoA, ActII-orf4, CcaR, and RedD) belonging to the Streptomyces antibiotic regulatory protein (SARP) family. Both ORFs are separated by a 1.9-kb, apparently noncoding region. Replacement of the mtmR region by an antibiotic resistance cassette completely abolished mithramycin biosynthesis. Expression of mtmR in a high-copy-number vector in S. argillaceus caused a 16-fold increase in mithramycin production. The mtmR gene restored actinorhodin production in Streptomyces coelicolor JF1 mutant, in which the actinorhodin-specific activator ActII-orf4 is inactive, and also stimulated actinorhodin production by Streptomyces lividans TK21. A 241-bp region located 1.9 kb upstream of mtmR was found to be repeated approximately 50 kb downstream of mtmR at the other end of the mithramycin gene cluster. A model to explain a possible route for the acquisition of the mithramycin gene cluster by S. argillaceus is proposed.
Lombó
F
F
Departamento de Biología Funcional e Instituto Universitario de Biotecnología de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain.
Braña
A F
AF
Méndez
C
C
Salas
J A
JA
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D002240:Carbohydrate Sequence; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D016384:Consensus Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D005809:Genes, Regulator; D008969:Molecular Sequence Data; D015394:Molecular Structure; D005810:Multigene Family; D016366:Open Reading Frames; D008926:Plicamycin / Q000096:biosynthesis* / Q000737:chemistry; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013302:Streptomyces / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C117104:MtmR protein, Streptomyces argillaceus; D015534:Trans-Activators; D008926:Plicamycin