N-type inactivation of the Kv1.2 voltage-gated potassium channel is a process in which the N-terminal of the protein (its first 20 amino acids) binds to the open-channel surface, extends and occludes its pore. This process has been experimentally studied in both intact and ShBDelta6-46 channels in which the inactivating peptides are supplied in the bath solution. In this work we provide a qualitative description of N-type inactivation by simulating the random walk of charged inactivating peptides in the electrostatic field that originates from the charges present in the channel and in the cellular membrane. Our results give a deeper insight into the previously reported influence of electrostatics on the rate of N-type inactivation of ShBDelta6-46. We also show how the enchaining of the peptides, i.e., considering the intact form of the channel, influences the N-type inactivation with different charges of those peptides.

Ion channels are large transmembrane proteins that are able to conduct small inorganic ions. They are characterized by high selectivity and the ability to gate, i.e. to modify their conductance in response to different stimuli. One of the types of gating follows the ball and chain model, according to which a part of the channel's protein forms a ball connected with the intracellular side of the channel by a polypeptide chain. The ball is able to modify the conductance of the channel by properly binding to and plugging the channel pore. In this study, the polypeptide ball is treated as a Brownian particle, the movements of which are limited by the length of the chain. The probability density of the ball's position is resolved by different diffusional operatorsparabolic (including the case with drift), hyperbolic, and fractional. We show how those different approaches shed light on different aspects of the movement. We also comment on some features of the survival probabilities (which are ready to be compared with electrophysiological measurements) for issues based on the above operators.