Modulation of the I channel by PIP requires two binding sites per monomer.

The phosphatidyl-inositol-4,5-bisphosphate (PIP) lipid has been shown to be crucial for the coupling between the voltage sensor and the pore of the potassium voltage-gated K7 channel family, especially the K7.1 channel. Expressed in the myocardium membrane, K7.1 forms a complex with KCNE1 auxiliary subunits to generate the I current. Here we present molecular models of the transmembrane region of this complex in its three known states, namely the Resting/Closed (RC), the Intermediate/Closed (IC), and the Activated/Open (AO), robustness of which is assessed by agreement with a range of biophysical data. Molecular Dynamics (MD) simulations of these models embedded in a lipid bilayer including phosphatidyl-inositol-4,5-bisphosphate (PIP) lipids show that in presence of KCNE1, two PIP lipids are necessary to stabilize each state. The simulations also show that KCNE1 interacts with both PIP binding sites, forming a tourniquet around the pore and preventing its opening. The present investigation provides therefore key molecular elements that govern the role of PIP in KCNE1 modulation of I channels, possibly a common mechanism by which auxiliary KCNE subunits might modulate a variety of other ion channels.