The voltage sensor and the gate in ion channels

Abstract

This chapter illustrates two aspects of ion channels: the gating process and the transduction from the initiating stimulus to the operation of the gate. The gating process is the operation of the gate proper while the transducer may be considered the sensor of the stimulus that ultimately opens and closes the channel. It also addresses one type of sensor: the membrane potential or voltage sensor. The understanding of voltage sensing and gating has been the result of a large number of physiological and biophysical observations that were initiated by the pioneering work of Hodgkin and Huxley in a large variety of ion channels from squid axon sodium and potassium channels to potassium channels from bacteria. The correlation between structure and function has benefited especially from the possibility of expressing ion channels in heterologous expression systems that allows the study of specially engineered channels where specific sites can be tested with EPR or fluorescent probes.