Predictions of the ball and chain model of channel inactivation

Voltage gated ion channels activate in response to step changes in voltage but slowly inactivate even though the voltage is maintained. It has been proposed that part of the channel forms a ball tethered to a chain and inactivation occurs when this ball binds to a site blocking the pore of the channel. The authors derived the statistical properties of this model so that it can be quantitatively tested by single-channel experiments on mutant channels with chains of different lengths. The model predicts that the distribution of the times for the ball to reach the binding site is a single exponential, with a rate constant that is inversely proportional to the square of the length of the chain.< >