ISOLATION, CHARACTERIZATION, AND MAPPING OF 2 HUMAN POTASSIUM CHANNELS

Two novel human genes encoding putative potassium channels, kH1 and kH 2, were identified from a human fetal brain cDNA library. Sequence ana lysis showed that kH1 and kH2 are homologous to rat IK8 and rat K13, r espectively. The kH1 encodes a polypeptide of 495 amino acids, which s hares 88% and 95% identity to IK8 at the nucleotide and amino acid lev el, respectively. The kH2 encodes a polypeptide of 515 amino acids wit h 86% and 92% identity to K13 at the nucleotide and amino acid level, respectively. Northern blot studies revealed that one mRNA species, ap proximately 5kb, of the kH1 was expressed abundantly in tissues examin ed, including the heart, skeletal muscle, and less abundant in the bra in, liver, kidney, and pancreas. Interestingly, an alternative spliced form of 2.4 kb mRNA species of the kH1 was also found in the brain. U nlike kH1, 2.4 kb of kH2 was expressed predominantly in the brain, pla centa, and the skeletal muscle where it shared a differently spliced f orm of the kH2 mRNA, approximately 2.0 kb. Fluorescence in situ hybrid ization localized kH1 to the human chromosome 2p25 and kH2 to the huma n chromosome 20q13. (C) 1997 Academic Press.