Defining how multiple lipid species interact with inward rectifier potassium (Kir2) channels.

Protein-lipid interactions are a key element of the function of many integral membrane proteins. These potential interactions should be considered alongside the complexity and diversity of membrane lipid composition. Inward rectifier potassium channel (Kir) Kir2.2 has multiple interactions with plasma membrane lipids: Phosphatidylinositol (4, 5)-bisphosphate (PIP) activates the channel; a secondary anionic lipid site has been identified, which augments the activation by PIP; and cholesterol inhibits the channel. Molecular dynamics simulations are used to characterize in molecular detail the protein-lipid interactions of Kir2.2 in a model of the complex plasma membrane. Kir2.2 has been simulated with multiple, functionally important lipid species. From our simulations we show that PIP interacts most tightly at the crystallographic interaction sites, outcompeting other lipid species at this site. Phosphatidylserine (PS) interacts at the previously identified secondary anionic lipid interaction site, in a PIP concentration-dependent manner. There is interplay between these anionic lipids: PS interactions are diminished when PIP is not present in the membrane, underlining the need to consider multiple lipid species when investigating protein-lipid interactions.