A human genomic library was constructed and screened with hybridization probes derived from sheep and rat cDNAs encoding the a and a(+) isoforms, respectively, of the Na',K+-ATPase catalytic subunit. Genomic sequences spanning 150 kilobases were isolated. Four genes, designated aA, aB, aC, and aD, each 20-25 kilobases in length, were identified by restriction mapping, Southern blot hybridization analysis, and limited DNA sequencing. We present evidence that two of these genes, aA and aB, encode the a and a(+) isoforms, respectively. The other genes, aC and aD, one of which is physically linked to the a(+) gene, exhibit nucleotide and amino acid homology to Na+,K+-ATPase catalytic subunit cDNA sequences but do not correspond to any previously identified isoforms.The Na+,K+-ATPase is an integral membrane protein responsible for establishing and maintaining the electrochemical gradients of Na+ and K+ across the plasma membrane of animal cells. As these gradients are essential for osmoregulation, Na+-coupled transport of a variety of organic and inorganic molecules, and electrical excitability of nerve and muscle, the enzyme plays a central role in cellular physiology. It is composed of two subunits, a large catalytic subunit (a) and a smaller glycoprotein subunit (f3) ofunknown function.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.