CONVERSION OF A DELAYED RECTIFIER K-GATED INWARD RECTIFIER K+ CHANNELBY 3 AMINO-ACID SUBSTITUTIONS( CHANNEL TO A VOLTAGE)

Single, double, and triple mutations progressively shift Shaker activa tion to more hyperpolarized potentials, resulting in an increase in th e fraction of inactivated channels at negative resting voltages. The m ost negatively shifted mutation, the triple mutant, behaves like an in ward rectifier. What is usually considered activation for an inward re ctifier is, for the triple mutant, recovery from inactivation, and wha t is usually considered deactivation is inactivation. This conversion from outward rectifier to inward rectifier does not rely on a differen ce in sign or direction of charge movement of the voltage sensor, sinc e activation of the Shaker outward rectifier is due to a different gat e than activation of the triple mutant inward rectifier. Other voltage -dependent inward rectifiers in the Shaker family may work by a simila r mechanism.