Transport mechanism and pH regulation of the Na+/H+ antiporter NhaA from Escherichia coli: an electrophysiological study.

ABSTRACT: Using an electrophysiological assay the activity of NhaA was tested in a wide pH range from pH 5.0 to 9.5. Forward and reverse transport directions were investigated at zero membrane potential using preparations with inside-out and right side-out-oriented transporters with Na(+) or H(+) gradients as the driving force. Under symmetrical pH conditions with a Na(+) gradient for activation, both the wt and the pH-shifted G338S variant exhibit highly symmetrical transport activity with bell-shaped pH dependences, but the optimal pH was shifted 1.8 pH units to the acidic range in the variant. In both strains the pH dependence was associated with a systematic increase of the K(m) for Na(+) at acidic pH. Under symmetrical Na(+) concentration with a pH gradient for NhaA activation, an unexpected no

SUBMITTER: Mager T 

PROVIDER: S-EPMC3123120 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature