Primary structure and functional expression of the beta sub(1) subunit of the rat brain sodium channel

Complementary DNA clones encoding the beta sub(1) subunit of the rat brain sodium channel were isolated by a combination of polymerase chain reaction and library screening techniques. The deduced primary structure indicates that the beta sub(1) subunit is a 22,851-dalton protein that contains a single putative transmembrane domain and four potential extracellular N-linked glycosylation sites, consistent with biochemical data. Northern blot analysis reveals a 1400-nucleotide messenger RNA in rat brain, heart, skeletal muscle, and spinal cord. Coexpression of beta sub(1) subunits with alpha subunits increases the size of the peak sodium current, accelerates its inactivation, and shifts the voltage dependence of inactivation to more negative membrane potentials.