REGULATION OF THE ACTIVITY OF VOLTAGE-GATED POTASSIUM CHANNELS BY BETA-SUBUNITS

Voltage-gated potassium channels may consist of two distinct types of subunits assembled in heteromultimeric complexes. One type of subunit, the alpha subunits, are sufficient to form the ion channel pore and the principal channel gating machinery. The second type of subunit, the beta subunits, may have an auxiliary function, in particular in mediating rapid inactivation of voltage-gated potassium channels. Therefore, different alpha/beta subunit compositions may generate voltage-gated potassium channels with properties distinct from the ones which are expressed by alpha subunits alone. The primary sequences of alpha subunits are structurally related and belong to a gene superfamily which may have evolved from a primordial ion channel gene. Similarly, beta-subunit-related primary sequences have been identified in plants as well as in procaryotes. Possibly, primordial potassium channel were already assembled from alpha and beta subunits.