By regulating transmembrane Na+ and K+ concentrations and membrane potential, the Na+,K+-ATPase plays an important role in regulating cardiac, skeletal, and smooth muscle function. A high degree of amino acid sequence and structural identity characterizes the three Mr 100,000 Na+,K+-ATPase α subunit isoforms expressed in cardiac and skeletal muscle. Strikingly, vascular smooth muscle utilizes alternative RNA processing of the α-1 gene to express a structurally distinct Mr ∼65,000 isoform, α-1-T (truncated). Analysis of both its mRNA and protein structure reveals that α-1-T encodes only the first 554 amino acids of α-1 to Gly554, then terminates with an intron-encoded 27-residue peptide. By Western blot analysis, α-1-T represents a major, evolutionarily conserved, truncated Na+,K+-ATPase isoform expressed in vascular smooth muscle. This demonstrates an unexpected complexity in the regulation of vascular smooth muscle Na+,K+-ATPase gene expression and suggests that a structurally novel, truncated a subunit may play a role in vascular smooth muscle active ion transport.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Biological Chemistry|
|State||Published - Sep 25 1991|
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