title: Expression of a sodium proton antiporter (NhaA) in Escherichia coli is induced by Na+ and Li+ ions.
abstract: Regulation of expression of nhaA, the gene which encodes a Na+/H+ antiporter in Escherichia coli has been studied. Two promoters have been identified in the upstream sequence of the gene and the corresponding start point of transcription mapped by primer extension. Monitoring the beta-galactosidase activity of a chromosomal translation fusion of nhaA'-'lacZ show that at pH 7.5 the gene is induced, within 1 h, by 100 mM of either Li+ or Na+. Change of pH between 6.5 and 8.5 by itself does not increase expression of the gene but it markedly increases the sensitivity of the expression system to the ions. At pH 7.5 maximal induction is obtained by 100 mM NaCl, whereas at pH 8.6, 10 mM NaCl elicit similar response. The pattern of regulation of nhaA reflects its importance in adaptation to high salinity and alkaline pH in E. coli.
authors.affiliation: Division of Microbial and Molecular Ecology, Hadassah Medical School, Hebrew University of Jerusalem, Israel.
authors.forename: R
authors.initials: R
authors.lastname: Karpel
authors.forename: T
authors.initials: T
authors.lastname: Alon
authors.forename: G
authors.initials: G
authors.lastname: Glaser
authors.forename: S
authors.initials: S
authors.lastname: Schuldiner
authors.forename: E
authors.initials: E
authors.lastname: Padan
mesh_terms: D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D012964:Sodium / Q000494:pharmacology*; D017923:Sodium-Hydrogen Exchangers; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D017923:Sodium-Hydrogen Exchangers; D008094:Lithium; D012964:Sodium; D001616:beta-Galactosidase