Transcriptional organization and regulation of an antibiotic export complex in the producing Streptomyces culture

Abstract

Three open reading frames (ORFs) in the actII region of the actinorhodin biosynthetic gene cluster of Streptomyces coelicolor A3(2), which are involved in the export of the antibiotic are carried on two divergent transcripts. A monocistronic transcript carries actII-ORF1, encoding a putative repressor protein, and a bicistronic transcript codes for actII-ORF2 and -ORF3, whose products have been postulated to form an antibiotic export complex. The actII-ORF1 and actII-ORF2/3 transcripts each have a single promoter and the promoters for the two transcripts overlap. Both promoters are most active in cultures that have developed to the stage of actinorhodin production. The promoters resemble consensus promoters of the vegetative class in Escherichia coli and Streptomyces. We also demonstrate that these promoters are expressed in E. coli and use this finding to reveal a regulatory role for the repressor, using the xylE reporter gene on promoter-probe shuttle vectors and regulated expression of the actII-ORF1 gene under control of Plac. The actII-ORF2/3 promoter is strongly repressed by the ORF1 product and the ORF1 product also represses its own promoter. The finding that the operator/promoter arrangement, and regulatory interconnection, of an antibiotic export/repressor gene pair in Streptomyces strikingly resemble those for tetracycline resistance in bacteria of clinical importance supports the hypothesis of an evolutionary origin of such genes in an ancestral actinomycete.

Regulation of the Streptomyces coelicolor Calcium-Dependent Antibiotic by absA , Encoding a Cluster-Linked Two-Component System

“…5). Further experimentation will be required to determine whether SCE22.23c is involved in the export of CDA and whether its expression is regulated by the product of SCE22.24c, as is the case for actII-ORF1/ORF2 in S. coelicolor (11) and tcmR/tcmA in Streptomyces glaucescens GLA.0 (24).…”

Identification of a monooxygenase from Streptomyces coelicolor A3(2) involved in biosynthesis of actinorhodin: purification and characterization of the recombinant enzyme

“…We have chosen to investigate the enzymes involved in the later oxidative steps of the biosynthesis of actinorhodin that are encoded within the actVA and actVB regions of the act biosynthetic cluster (3,4,7). Previously, we have overexpressed the gene product of the actVB region and shown it to be a flavin mononucleotide:NADH oxidoreductase (15).…”

Sequence and transcriptional analysis of the Streptomyces glaucescens tcmAR tetracenomycin C resistance and repressor gene loci

“…There has also been some speculation on the regulation and regulatory roles of resistance genes relative to antibiotic production genes (23), but to date, only limited information exists on the relationship between the expression of antibiotic production and resistance genes in Streptomyces species (9,30).…”