Figure 7. Effects of pH on transient and transport-associated currents in wild-type and mutated isoforms.

A, changing the pH as indicated does not significantly alter either the transient (Aa) or the transport-associated (Ab) currents. On the contrary, in the mutated form, the asymmetry of the transient currents seen at pH 7.6 is increased at pH 9.0 and decreased at pH 6.5 (Ba). Furthermore, the transport-associated current is strongly impaired at pH 9.0 and, in this condition, the pre-steady-state currents are not completely abolished (Bb). Voltage pulses to −120, −80, 0 and +40 mV from V_h = −40 mV; pulse duration was 200 ms.