Complex interactions among residues within pore region determine the K+ dependence of a KAT1-type potassium channel AmKAT1

Abstract

Summary KAT1-type channels mediate K+ influx into guard cells that enables stomatal opening. In this study, a KAT1-type channel AmKAT1 was cloned from the xerophyte Ammopiptanthus mongolicus. In contrast to most KAT1-type channels, its activation is strongly dependent on external K+ concentration, so it can be used as a model to explore the mechanism for the K+-dependent gating of KAT1-type channels. Domain swapping between AmKAT1 and KAT1 reveals that the S5-pore-S6 region controls the K+ dependence of AmKAT1, and residue substitutions show that multiple residues within the S5-Pore linker and Pore are involved in its K+-dependent gating. Importantly, complex interactions occur among these residues, and it is these interactions that determine its K+ dependence. Finally, we analyzed the potential mechanism for the K+ dependence of AmKAT1, which could originate from the requirement of K+ occupancy in the selectivity filter to maintain its conductive conformation. These results provide new insights into the molecular basis of the K+-dependent gating of KAT1-type channels. Significance Statement This work investigates the molecular basis of the K+ dependence of AmKAT1 and provides new insight into the mechanisms of the K+-dependent gating in plant KAT1-type channels.