Docking simulation of a PIP2 analogue with the helix A-B linker of Kv7.3 predicts an interaction that is strongly weakened by charge-reversal mutations. (A) Left: Shown is an expanded view of the results of the docking simulation of the short-chain PIP2 analogue, GPMI-P2, docked to the top of the wt Kv7.3 helix A-B linker, with the residues with which it is predicted to make interactions indicated. Center: Superimposed are the electrostatic profile of the putative PIP2-interacting surface of the wt Kv7.3 helix A-B linker with GPMI-P2. Blue and red are positive and negative electrostatic surface potentials of more than ±15kT/e, respectively, and the electron density maps of the oxygens of each phosphate group of the GPMI-P2 are shown as red wire spheres. Right: Shown are interactions between GPMI-P2 and the top of the modeled wt linker predicted by the docking simulation. Superimposed is the GPMI-P2 molecule with the residues of the linker with which it makes hydrogen bonds, indicated by dotted green lines. (B) Shown are (left) an expanded view of the results of the docking simulation of GPMI-P2 docked to the top of the KKR-EEE mutant Kv7.3 helix A-B linker, (center) the electrostatic profile of the putative PIP2-interacting surface of the KKR-EEE mutant Kv7.3 helix A-B linker superimposed with GPMI-P2, and (right) interactions between GPMI-P2 and the top of the modeled KKR-EEE mutant linker predicted by the docking simulation. The interacting channel residues and the P1, P4, and P5 phosphates of GPMI-P2 are labeled. Orange, phosphorus; red, oxygen; purple, nitrogen, white, carbon or hydrogen.
