Human and rodent MaxiK channel beta-subunit genes: Cloning and characterization

Voltage- and Ca2+-sensitive K+ (MaxiK) channels play hey roles in controlli ng neuronal excitability and vascular tone. We cloned and analyzed human an d rodent genes for the modulatory beta subunit, KCNMB1. The human and mouse beta-subunit genes are similar to 11 and similar to 9 kb in length, respec tively, and have a four exon-three intron structure. Primer extension assay localized the transcription initiation site at 442 (human) or 440 (mouse) bp upstream of the translation initiation codon, agreeing with the transcri pt size in Northern blots, Both genes have a TATA-less putative promoter re gion, with a transcription initiator-like region, and motifs characteristic of regulated promoters, including muscle-specific enhancing factors-1 and -2. Consistent with a tissue-specific expression of KCNMB1, regulated at th e transcriptional level, beta-subunit transcripts are abundant in smooth mu scle and heart, but scarce in lymphatic tissues, brain, and liver. Expresse d rat and mouse beta subunits increase the apparent Ca2+ sensitivity of the human MaxiK channel alpha subunit. (C) 1999 Academic Press.