mprA, an Escherichia coli gene that reduces growth-phase-dependent synthesis of microcins B17 and C7 and blocks osmoinduction of proU when cloned on a high-copy-number plasmid

Abstract

Microcins B17 and C7 are plasmid-determined, peptide antibiotics produced by Escherichia coli when cells enter the stationary phase of growth. Microcinogenic strains are immune to the action of the microcin they synthesize. A well-characterized deficient-immunity phenotype is exhibited by microcin B17-producing cells in the absence of the immunity gene mcbG (M.C. Garrido, M. Herrero, R. Kolter, and F. Moreno, EMBO J. 7:1853-1862, 1988). A 14.6-kilobase-pair EcoRI chromosomal fragment was isolated by its ability to suppress this phenotype when cloned into a multicopy vector. This fragment was mapped to 57.5 min on the E. coli genetic map. The position of the gene responsible for suppression, designated mprA, was determined by insertional mutagenesis and deletion analysis. mprA was shown to be transcribed clockwise on the E. coli chromosome, and its product was identified as a 19-kilodalton polypeptide. Suppression was shown to be achieved by decreasing microcin B17 production. Increased mprA gene dosage also caused a decrease in microcin C7 production and blocked the osmoinduction of the proU locus in high-osmolarity media. Our results suggest that the mprA gene product could play a regulatory role on expression of several E. coli genes, this control being exerted at the transcriptional level.

EmrR is a negative regulator of the Escherichia coli multidrug resistance pump EmrAB

“…The mprA (emrR) gene that is adjacent to emrA has a typical putative rho-independent terminator and was ascribed the function of regulating expression of microcin synthesis (4). The use of lacZ fusions to systematically search for the promoter of the operon led to the unexpected finding that emrR was actually a part of the emrAB operon.…”

“…This suggested that expression of emrAB can be induced by CCCP. We report here that the emrAB transcription initiates from the regulatory region of a previously described gene, mprA (4), that the expression of emrAB can be induced by several structurally unrelated compounds, and that mprA encodes a repressor of the pump synthesis. Some of the chemicals that induce this operon serve as substrates for the pump.…”

Analysis of RovA, a Transcriptional Regulator of Yersinia pseudotuberculosis Virulence That Acts through Antirepression and Direct Transcriptional Activation

“…A). A prototypic member of the entire regulator family is MarR, a repressor of the marROAB operon mediating intrinsic multiple antibiotic resistance in E. coli (17,18). To date, the crystal structures of three MarR-like proteins have been determined without their DNA targets.…”

Nucleotide sequence of the Escherichia coli regulatory gene mprA and construction and characterization of mprA-deficient mutants

“…All of these effects appeared to be exerted at the transcriptional level. On the basis of these data and other evidence, we proposed that the mprA gene product (19 kDa) could play a regulatory role in the transcription of several E. coli genes (5). To further characterize mprA and to assess its presumed regulatory effects, we have examined the expression of mcb, mcc, and proU operons in null mprA mutants.…”

“…A 742-bp DNA fragment containing mprA was sequenced by the dideoxy chain termination method (27). We took advantage of the collection of mprAlacZ fusions, generated by the insertion of the miniMudII1681 transposon (5) (Fig. 1A), to obtain convenient fragments to be sequenced.…”