Residue Aspartate-147 from the Third Transmembrane Region of Na(+)/H(+) Antiporter NhaB of Vibrio alginolyticus Plays a Role in Its Activity

NhaB is a bacterial Na(+)/H(+) antiporter with unique topology. The pH dependence of NhaB from Vibrio alginolyticus differs from that of the Escherichia coli NhaB homolog. Replacement of Asp-147 with Glu made high H(+) concentrations a requirement for the NhaB activity. Replacement of Asp-147 with neutral amino acids inactivated NhaB.