Time, voltage and ionic concentration dependence of rectification of h-erg expressed in Xenopus oocytes

The rapid delayed rectifier, I-Kr, is believed to have h-erg (human ether-a-go-go related gene) as its molecular basis, A recent study has shown that rectification of h-eg involves a rapid inactivation process that involves rapid closure of the external mouth of the pore or C-type inactivation, We measured the instantaneous current to voltage relationship for h-erg channels using the saponin permeabilized variation of the cut-open oocyte clamp technique, In contrast to C-type inactivation in other voltage-gated KC channels, the rate of inactivation was strongly voltage dependent at depolarized potentials, This voltage dependence could be modulated independently of activation by increasing [K+](o) from 2 to 98 mM, These results suggest that inactivation of h-erg has its own intrinsic voltage sensor.