Biomaterial Database

Physiological role of nhaB, a specific Na+/H+ antiporter in Escherichia coli. 1993

E Pinner, and Y Kotler, and E Padan, and S Schuldiner

Division of Microbial and Molecular Ecology, Hebrew University of Jerusalem, Israel.

The nhaB gene which codes for Na+/H+ antiporter activity in Escherichia coli was recently cloned (Pinner, E., Padan, E., and Schuldiner, S. (1992) J. Biol. Chem. 267, 11064-11068). In order to elucidate the role of nhaB in Na+ and H+ ions physiology and its interaction with nhaA, we generated mutants in which the chromosomal gene has been inactivated by insertion/deletion. A mutant devoid of both nhaA and nhaB is extremely sensitive to Na+ and Li+ at all pH values, and membranes prepared from this strain show no Na+/H+ antiporter activity. As opposed with the delta nhaA mutant which contains NhaB, the pH independent Na+/H+ antiporter (Padan, E., Maisler, N., Taglicht, D., Karpel, R., and Schuldiner, S. (1989) J. Biol. Chem. 264, 20297-20302), the delta nhaB mutant, containing NhaA, shows Na+/H+ antiporter activity highly dependent on pH. nhaB, in the absence of nhaA, confers a certain tolerance to Na+ which decreases with increasing pH. In the absence of NhaB, NhaA alone confers complete halotolerance under all conditions tested. However, when grown on agar in minimal medium on substrates which are symported with Na+ (proline, serine, and glutamate) at pH 6 and at low Na+ concentrations (< 10 mM), delta nhaB grows slower than the wild type and its Na+ dependent transport of glutamate and proline is markedly inhibited. Since both of these defects of the delta nhaB strain are alleviated upon transformation of the mutant with multicopy plasmid bearing nhaA, we conclude that nhaB is crucial when the level of NhaA activity is growth limiting, when nhaA is not sufficiently induced, and/or when NhaA is not activated.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008094	Lithium	An element in the alkali metals family. It has the atomic symbol Li, atomic number 3, and atomic weight [6.938; 6.997]. Salts of lithium are used in treating BIPOLAR DISORDER.	Lithium-7,Lithium 7
D010957	Plasmids	Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.	Episomes,Episome,Plasmid
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D011392	Proline	A non-essential amino acid that is synthesized from GLUTAMIC ACID. It is an essential component of COLLAGEN and is important for proper functioning of joints and tendons.	L-Proline,L Proline
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D004262	DNA Restriction Enzymes	Enzymes that are part of the restriction-modification systems. They catalyze the endonucleolytic cleavage of DNA sequences which lack the species-specific methylation pattern in the host cell's DNA. Cleavage yields random or specific double-stranded fragments with terminal 5'-phosphates. The function of restriction enzymes is to destroy any foreign DNA that invades the host cell. Most have been studied in bacterial systems, but a few have been found in eukaryotic organisms. They are also used as tools for the systematic dissection and mapping of chromosomes, in the determination of base sequences of DNAs, and have made it possible to splice and recombine genes from one organism into the genome of another. EC 3.21.1.	Restriction Endonucleases,DNA Restriction Enzyme,Restriction Endonuclease,Endonuclease, Restriction,Endonucleases, Restriction,Enzymes, DNA Restriction,Restriction Enzyme, DNA,Restriction Enzymes, DNA
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D005798	Genes, Bacterial	The functional hereditary units of BACTERIA.	Bacterial Gene,Bacterial Genes,Gene, Bacterial
D005971	Glutamates	Derivatives of GLUTAMIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the 2-aminopentanedioic acid structure.	Glutamic Acid Derivatives,Glutamic Acids,Glutaminic Acids