[Molecular and biophysical aspects of cardiac Na channel]

Voltage-dependent ion channels mediate action potential and conduction in cardiac cells. In the past ten years, their single channel properties and protein components have been identified, isolated and restored to functional form in the purified state. Na channel has a primary alpha subunit, which is composed of four homologous domains, each of which has six transmembrane segments. Site-directed mutation has probed the function of specific regions or even of single amino acids. The ion-conducting pore, molecular voltmeter, ion filter and regulatory system of sodium channel have been characterized by coordination of biophysical, biochemical and molecular genetic methods.