A Bubble Model for the Gating of Kv Channels

Abstract

Voltage-gated K v channels play fundamental roles in many biological processes, such as the generation of the action potential. The gating mechanism of K v channels is characterized experimentally by single-channel recordings and ensemble properties of the channel currents. In this work, we propose a bubble model coupled with a Poisson-Nernst-Planck (PNP) system to capture the key characteristics, particularly the delay in the opening of channels. The coupled PNP system is solved numerically by a finite-difference method and the solution is compared with an analytical approximation. We hypothesize that the stochastic behaviour of the gating phenomenon is due to randomness of the bubble and channel sizes. The predicted ensemble average of the currents under various applied voltage across the channels is consistent with experimental observations, and the Cole-Moore delay is captured by varying the holding potential.

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“…Of course, other possibilities exist. Alternating access might arise, for example, from bubbles in the conduction pathway, which we are studying in another work [95]. Two bubbles might act as coupled activation and inactivation gates, correlated to provide alternating access to an occluded state, for example.…”