Disease relevance of nhaB

• Physiological role of nhaB, a specific Na+/H+ antiporter in Escherichia coli [1].
• Here we identified two additional antiporter genes, designated Vc-nhaB and Vc-nhaD, encoding two putative proteins of 530 and 477 residues, respectively, highly homologous to the respective antiporters of Vibrio species and E. coli [2].
• It has previously been shown that functional expression of CcrA, a metallo-beta-lactamase from Bacteroides fragilis, in Escherichia coli requires a mutation in either dsbA or dsbB, components of a periplasmic disulfide bond-catalyzing system [3].

High impact information on nhaB

• By comparing the phenotypes conferred by plasmids bearing the various mutations to the phenotype of the wild type upon transformation of strains NM81 (delta nhaA) or EP432 (delta nhaA, delta nhaB) we found that none of the NhaA histidines are essential for the Na+/H+ antiporter activity of the NhaA protein [4].
• Membranes from a dsbB null mutant display no DsbA reoxidation activity [5].
• 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 [1].
• Observing folding pathways and kinetics of a single sodium-proton antiporter from Escherichia coli [6].
• Sod2 is the sodium-proton antiporter on the plasma membrane of the fission yeast Schizosaccharomyces pombe [7].

Chemical compound and disease context of nhaB

• We replaced each of these Asp residues by Asn in plasmid encoded nhaA and expressed these constructs in an E. coli mutant defective in both nhA and nhaB [8].

Biological context of nhaB

• Later, it was concluded that the defective Na+/H+ antiporter in the mutant was the NhaB system, and the nhaB gene was mapped to 25.6 min on the E. coli chromosome [Thelen, P., Tsuchiya, T., and Goldberg, E.B. (1991) J. Bacteriol. 173, 6553-6557] [9].
• When nhaB was deleted, the fusion gene was expressed at pH values below 8, while the expression was observed at alkaline pH after chaA was deleted [10].
• The Na+ sensitivity of the delta nhaA delta nhaB mutant bearing the H226R-NhaA plasmid at alkaline pH provided a very powerful tool to isolate revertants and suppressants of H226R growing on high Na+ at alkaline pH [11].

Anatomical context of nhaB

• Membranes from cells containing multiple dose of nhaB display enhanced Na+/H+ antiporter activity, as measured by the ability of Na+ to collapse a preformed pH gradient or by direct measurement of 22Na+ fluxes [12].

Other interactions of nhaB

• CONCLUSION: pH regulates a core set of genes independently of oxygen, including yagU, fimbriae, periplasmic chaperones, and nhaB [13].
• 0. Mutants with defects in nhaB grow normally on agar media containing 0.5 M NaCl, but nhaA mutants are sensitive to 0.5 M NaCl [14].
• To examine this hypothesis, we applied the phoA fusion method to the cloned nhaB gene [15].

Analytical, diagnostic and therapeutic context of nhaB

• 5. Restriction mapping and a Southern blot analysis revealed that the cloned gene was different from the nhaA and the nhaB of V. parahaemolyticus [16].
• Controlled unfolding and refolding of a single sodium-proton antiporter using atomic force microscopy [17].

References