The putative Na+/H+ antiporter of Vibrio cholerae, Vc-NhaP2, mediates the specific K+/H+ exchange in vivo.

TitleThe putative Na+/H+ antiporter of Vibrio cholerae, Vc-NhaP2, mediates the specific K+/H+ exchange in vivo.
Publication TypeJournal Article
Year of Publication2010
AuthorsResch CT, Winogrodzki JL, Patterson CT, Lind EJ, Quinn MJ, Dibrov P, Häse CC
JournalBiochemistry
Volume49
Issue11
Pagination2520-8
Date Published2010 Mar 23
ISSN1520-4995
KeywordsBacterial Proteins, Biocatalysis, Cloning, Molecular, Hydrogen, Hydrogen-Ion Concentration, Potassium, Sequence Homology, Amino Acid, Sodium-Hydrogen Antiporter, Substrate Specificity, Vibrio cholerae
Abstract

The existence of bacterial K(+)/H(+) antiporters that prevent the overaccumulation of potassium in the cytoplasm was predicted by Peter Mitchell almost 50 years ago. The importance of K(+)/H(+) antiport for bacterial physiology is widely recognized, but its molecular mechanisms remain underinvestigated. Here, we demonstrate that a putative Na(+)/H(+) antiporter, Vc-NhaP2, protects cells of Vibrio cholerae growing at pH 6.0 from high concentrations of external K(+). Resistance of V. cholerae to Na(+) was found to be independent of Vc-NhaP2. When assayed in inside-out membrane vesicles derived from antiporter-deficient Escherichia coli, Vc-NhaP2 catalyzed the electroneutral K(+)(Rb(+))/H(+) exchange with a pH optimum of approximately 7.75 with an apparent K(m) for K(+) of 1.62 mM. In the absence of K(+), it exhibited Na(+)/H(+) antiport, albeit rather weakly. Interestingly, while Vc-NhaP2 cannot exchange Li(+) for protons, elimination of functional Vc-NhaP2 resulted in a significantly higher Li(+) resistance of V. cholerae cells growing at pH 6.0, suggesting the possibility of Vc-NhaP2-mediated Li(+)/K(+) antiport. The peculiar cation specificity of Vc-NhaP2 and the presence of its two additional paralogues in the same genome make this transporter an attractive model for detailed analysis of the structural determinants of the substrate specificity in alkali cation exchangers.

Alternate JournalBiochemistry