ANTIPORTER NhaA FROM ESCHERICHIA COLI. AN ELECTROPHYSIOLOGICAL STUDY*
نویسندگان
چکیده
gradient for activation, both the wt and the pH-shifted G338S variant exhibit highly symmetrical transport activity with bell shaped pH dependencies, 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 Km for Na + at acidic pH. Under symmetrical Na + concentration with a pH gradient for NhaA activation an unexpected novel characteristic of the antiporter was revealed; rather than being down regulated it remained active even at pH as low as 5. These data allowed to advance a transport mechanism based on competing Na + and H +
منابع مشابه
Transport Mechanism and pH Regulation of the Na+/H+ Antiporter NhaA from Escherichia coli
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 th...
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