Kir6.2 channel activity is regulated by interaction of transmembrane domains 1 and 2 through I167 in the bundle‐crossing gate

ATP‐sensitive potassium (K ATP ) channel in pancreatic β‐cells is composed of four pore‐forming inward rectifier potassium (Kir) 6.2 subunits and four regulatory sulfonylurea receptor (SUR) 1 subunits and regulate insulin secretion. Kir6.2 consists of a N‐terminal region, an outer transmembrane helix (TM1), an intramembrane region that functions as a potassium selectivity filter, an inner transmembrane helix (TM2) that forms a bundle‐crossing gate, and a C‐terminal cytoplasmic domain. Mutations in the Kir6.2 subunit can cause neonatal diabetes with severe neurological features (DEND syndrome). The DEND syndrome‐inducing I167L mutation of Kir6.2 increases the open probability ( P o ) of the K ATP channel. To investigate the gating mechanism impacted by this mutation in Kir6.2 alone, we used C‐terminus‐truncated Kir6.2 channels to ascertain the impact of I167 mutations on P o in Kir6.2 channels in the absence of SUR1. We found that I167L and I167F mutations showed an increased P o while the P o of other mutations (I167A, I167V) were unchanged when compared to wild‐type channels. By mutating residues in TM1 (W68, L72, F75) that may interact with I167, we found that a double mutation of I167L and F75A normalized the P o . These results would suggest that I167 may play an important role in stabilizing the open state of Kir6.2 channels.