Identification of the PIP 2 ‐binding site on Kir6.2 by molecular modelling and functional analysis

ATP‐sensitive potassium (K ATP ) channels couple cell metabolism to electrical activity by regulating K + fluxes across the plasma membrane. Channel closure is facilitated by ATP, which binds to the pore‐forming subunit (Kir6.2). Conversely, channel opening is potentiated by phosphoinositol bisphosphate (PIP 2 ), which binds to Kir6.2 and reduces channel inhibition by ATP. Here, we use homology modelling and ligand docking to identify the PIP 2 ‐binding site on Kir6.2. The model is consistent with a large amount of functional data and was further tested by mutagenesis. The fatty acyl tails of PIP 2 lie within the membrane and the head group extends downwards to interact with residues in the N terminus (K39, N41, R54), transmembrane domains (K67) and C terminus (R176, R177, E179, R301) of Kir6.2. Our model suggests how PIP 2 increases channel opening and decreases ATP binding and channel inhibition. It is likely to be applicable to the PIP 2 ‐binding site of other Kir channels, as the residues identified are conserved and influence PIP 2 sensitivity in other Kir channel family members.