Figure 7. Permeation features for the wild-type and mutant channels.

(a) The conductance of the wild-type (left) and mutant (right) channels as a function of the membrane potential at 150 mM K⁺. The total conductance is nearly flat for the wild-type channel, but it is attenuated at the positive potentials or inward-rectified for the mutant channel. In the wild-type channel, the underlying conductances of the cycle fluxes indicate that the voltage-dependent increasing (cycle c) and decreasing (cycle a and b) cycles compensate for yielding a nearly constant conductance. In the mutant channel, cycle a is attenuated substantially, and the remaining cycles b and c generate attenuated conductance at positive potentials. (b) The relative flux contributions to conductance by various cycles in the wild-type (left) and mutant (right) channels at various [K⁺].