Complex interactions among residues within pore region determine the K + dependence of a KAT 1‐type potassium channel Am KAT 1

Summary KAT 1‐type channels mediate K + influx into guard cells that enables stomatal opening. In this study, a KAT 1‐type channel Am KAT 1 was cloned from the xerophyte Ammopiptanthus mongolicus . In contrast to most KAT 1‐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 KAT 1‐type channels. Domain swapping between Am KAT 1 and KAT 1 reveals that the S5–pore–S6 region controls the K + dependence of Am KAT 1, 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 Am KAT 1, 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 KAT 1‐type channels.