Family 8.A.5 - The Voltage Gated K+ Channel (beta subunit) Family       

Family ID: 52656

Many b-subunits of voltage-gated K+ channels (VIC superfamily, TC #1.A.1) have been sequenced and functionally characterized. The mammalian b-subunits are 350-410 residues in length. They exhibit extensive sequence similarity with many ubiquitous oxidoreductases, with bacterial stress response proteins and with plant auxin-induced proteins. These b-subunits are to some extent interchangeable, and a variety of alternative splice variants are found. They regulate various aspects of the voltage-gated mammalian channels as well as the Drosophila Shaker K+ channel. Thus they affect the voltage-dependence of the activation process, the rate of deactivation and both N-type and C-type inactivation. The conserved C-terminal domain of the b-subunit interacts with the conserved N-terminal hydrophilic domain of the Shaker a-subunit, the same region that determines the compatibility of a-subunits. The hyperkinetic gene of Drosophila encodes a b-subunit of 546 amino acyl residues that when defective produces the Shaker-like, ether-sensitive leg shaking.

Regulatory b-subunits of other channel proteins of the VIC superfamily (TC #1.A.1) function in distinct regulatory capacities, and some are non-homologous to members of the VICb family.