The effect of the conserved Leu/Ile site in the CD loop on the gating dynamics of Kir channels and corresponding micro-structural mechanism remains unclear. Molecular dynamics simulations were performed to investigate the structural mechanism of chicken Kir2.2. Compared to WT, the I223L mutant channel bound to PIP2 more strongly, was activated more rapidly, and maintained the activation state more stably after PIP2 dissociation. Cellular electrophysiology assays of mouse Kir2.1 and human Kir2.2 indicated that, consistent with simulations, the Leu residue increased the channel responses to PIP2 through increased binding affinity and faster activation kinetics, and the deactivation kinetics decreased upon PIP2 inhibition. The Ile residue induced the opposite responses. This difference was attributed to the distinct hydrophobic side chain symmetries of Leu and Ile; switching between these residues caused the interaction network to redistribute and offered effective conformation transduction in the Leu systems, which had more rigid and independent subunits.

http://dx.doi.org/10.1007/s12035-015-9466-x

MD simulations were performed at the Supercomputing Center of the Chinese Academy of Sciences (CAS) and at the National Supercomputer Center in Tianjin. This work was supported by National Natural Science Foundation of China grants 31230027, 11342002, 11372332,11247010, and 11475053, National Key Basic Research Foundation of China grant 2011CB710904, CAS Knowledge Innovation Program grant KJCX2-YW-L08, and Natural Science Foundation for Distinguished Young Scholars of the Hebei Province of China grant C2015202340.