Mapping of the physical interaction between the intracellular domains of an inwardly rectifying potassium channel, Kir6.2.

The amino-terminal and carboxyl-terminal domains of inwardly rectifying potassium (Kir) channel subunits are both intracellular. There is increasing evidence that both of these domains are required for the regulation of Kir channels by agents such as G-proteins and nucleotides. Kir6.2 is the pore-forming subunit of the ATP-sensitive K(+) (K(ATP)) channel. Using an in vitro protein-protein interaction assay, we demonstrate that the two intracellular domains of Kir6.2 physically interact with each other, and we map a region within the N terminus that is responsible for this interaction. "Cross-talk" through this interaction may explain how mutations in either the N or C terminus can influence the intrinsic ATP-sensitivity of Kir6.2. Interestingly, the "interaction domain" is highly conserved throughout the superfamily of Kir channels. The N-terminal interaction domain of Kir6.2 can also interact with the C terminus of both Kir6.1 and Kir2.1. Furthermore, a mutation within the conserved region of the N-terminal interaction domain, which disrupts its interaction with the C terminus, severely compromised the ability of both Kir6.2 and Kir2.1 to form functional channels, suggesting that this interaction may be a feature common to all members of the Kir family of potassium channels.