Osmotic induction of gene osmC expression in Escherichia coli K12.
osmC, an osmotically inducible gene of Escherichia coli, was physically mapped on the bacterial chromosome, cloned on multicopy plasmids, and its product, OsmC, was identified as a 14 kDa protein in maxicells. The DNA sequence of the gene and its upstream region were determined. The sequence of an osmC-phoA gene fusion confirmed the osmC reading frame. A deletion of osmC from the E. coli chromosome was constructed by gene replacement, demonstrating that it is not an essential gene. The osmCp promoter region was subcloned and a lac operon fusion transcribed under osmCp control was constructed. The expression of this operon fusion demonstrated that osmC regulation occurs at the transcriptional level. S1 nuclease protection experiments and deletion analysis identified two overlapping promoters with transcription start sites separated by ten nucleotides. All the sequences necessary for osmotic regulation of both promoters are located within a 137 base-pair DNA fragment extending from position -95 to +42 with respect to the putative osmC translation start. Two deletions were obtained that abolish the functioning of the upstream promoter. Yet, under our experimental conditions, the subsequent expression of the osmC-lacZ fusion was equivalent to that obtained from the tandem promoters. Mutations leading to constitutive expression of osmC were selected. Two independent mutations were obtained, both affected osmZ, the gene encoding the histone-like protein H1.
Gutierrez
C
C
Centre de Recherche de Biochimie et Génétique Cellulaire du CNRS, Toulouse, France.
Devedjian
J C
JC
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014882:Water-Electrolyte Balance
D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C099394:osmC protein, E coli; C070550:omcC protein, Geobacter sulfurreducens