Voltage-gated Na+ channels are heteromeric proteins consisting of α and β subunits. Although α subunits alone are sufficient to encode functional channels, β1 subunits appear to modulate the kinetics of inactivation. We have used a cross-species reverse transcriptase polymerase chain reaction approach to isolate cDNAs encoding a Na+ channel β1 subunit from human heart and skeletal muscle. The deduced amino acid sequence of the human β1 subunit exhibits 96% identity with the rat brain β1 subunit. Human β1 mRNA transcripts are abundantly expressed in skeletal muscle, heart, and brain. Genomic Southern blot hybridization experiments suggest that a single gene located on chromosome 19 encodes the human β1 subunit that is expressed in all three of these tissues. Co-expression of the human β1 subunit with the recombinant human skeletal muscle α subunit (hSkM1) in Xenopus oocytes results in Na+ currents that inactivate rapidly. In contrast, the human β1 subunit has no effect on the function of the tetrodotoxin-insensitive human heart Na+ channel (hH1). These findings indicate that the human β1 subunit is widely expressed but does not functionally modify all Na+ channel isoforms.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - Mar 11 1994|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology