A POTASSIUM CHANNEL BETA-SUBUNIT RELATED TO THE ALDO-KETO REDUCTASE SUPERFAMILY IS ENCODED BY THE DROSOPHILA HYPERKINETIC LOCUS

Genetic and physiological studies of the Drosophila Hyperkinetic (Hk) mutant revealed defects in the function or regulation of K+ channels e ncoded by the Shaker (Sh) locus, The Hk polypeptide, determined from a nalysis of cDNA clones, is a homologue of mammalian K+ channel beta su bunits (K-v beta). Coexpression of Hk with Sh in Xenopus oocytes incre ases current amplitudes and changes the voltage dependence and kinetic s of activation and inactivation, consistent with predicted functions of Hk in vivo. Sequence alignments show that Hk, together with mammali an K-v beta, represents an additional branch of the aldo-keto reductas e superfamily. These results are relevant to understanding the functio n and evolutionary origin of K-v beta.