Supra-physiological membrane potential induced conformational changes in K+ channel conducting system of skeletal muscle fibers.

The effects of a supra-physiological membrane potential shock on the conducting system of the delayed rectifier K(+) channels in the skeletal muscle fibers of frogs were studied. An improved double Vaseline gap voltage clamp technique was used to deliver stimulation pulses and to measure changes in the channel currents. Our results showed that a single 4 ms, -400 mV pulsed shock can cause a reduction in the K(+) channel conductance and a negative-shift of the channel open-threshold. Following the Boltzmann theory of channel voltage-dependence, we analyzed the shock-induced changes in the channel open-probability by employing both two-state and multi-state models. The results indicate a reduction in the number of channel gating particles after the electric shock, which imply possible conformational changes at domains that gate the channels proteins. This study provides further evidence supporting our hypothesis that high intensity electric fields can cause conformational changes in membrane proteins, most likely in the channel gating system. These structural changes in membrane proteins, and therefore their dysfunctions, may be involved in the mechanisms underlying electrical injury.