The KcsA Channel Cytoplasmic Domain Effects on the Inactivation Gating

Abstract

The KcsA channel is a representative potassium channel that is activated by changes in pH. Recently, we found that the cytoplasmic domain (CPD) acts as a pH-sensor by observing significant confirmation changes there in response to pH. These changes can influence the opening and closing of the KcsA channel. A selectivity filter region within the KcsA channel is also known to regulate gating by forming activation and inactivation states. However, it is not clear how the CPD and the selectivity filter region coordinate. We therefore made a mutant channel that has the wild-type filter and a CPD with all its negative charges neutralized. We found that this mutant had high activity independent of pH and no inactivation gating, indicating removal of negative charges in the CPD causes removal of inactivation. These results suggest that the CPD primarily regulates activation gating, and conformational changes of the CPD effects on the inactivation gating.