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

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.