A mutant KcsA channel that causes the same rubidium and potassium ions occupancy within the channel’s selectivity filter

Abstract

The crystal structure of KcsA reveals four perfectly coordinated K+-ions by the channel’s selectivity filter (SF). Interestingly, K+-channels also permeate Rb+-ions as well as they do K+-ions, albeit with a lower single channel conductance. Previously, the structure of KcsA in complex with Rb+-ions was solved and showed a sub-optimal number of ions bound to the SF (3 Rb+-ions) at the binding sites 1, 3 and 4. This observation was fundamental to explain the lower single channel conductance displayed by K+-channel in symmetrical rubidium.