Molecular cloning of three distinct forms of the Na+,K+-ATPase .alpha.-subunit from rat brain

Abstract

Rat brain and kidney cDNA libraries were constructed and screened with a cDNA insert corresponding to the mRNA for the sheep kidney Na+,K+-ATPase catalytic subunit. The alpha-subunit cDNAs isolated from the kidney library were derived from a single class of messenger RNA, and the brain cDNAs were derived from three classes of messenger RNA. The most abundant brain cDNA, which spans 5.1 kilobases, encodes the alpha(+) form of the enzyme. The second most abundant brain cDNA, which spans 3.65 kilobases, is identical with that of the kidney form and therefore encodes the alpha isoform. The third class of cDNA, which spans 3.55 kilobases, was present at low abundance and encodes an isoform of the alpha-subunit, designated alpha III, which has not been identified previously. The complete nucleotide sequence and deduced amino acid sequence for each of the brain and kidney cDNAs have been determined. In addition, we have identified a lysine-rich sequence that may function as a movable, ion-selective gate during cation binding and occlusion and have also identified several amino acid sequence variations that appear to explain some of the well-known species and tissue differences in cardiac glycoside sensitivity.

Regulation of blastocyst formation

“…The beta-subunit of M r 40-60 kD facilitates the processing and insertion of the alpha-subunit into the plasma membrane (138,145). In mammals these subunits are encoded by multi-gene families consisting of four alpha subunit genes (alpha1, alpha2, alpha3, alpha 4) and three beta subunit genes (beta 1, beta 2, beta 3), each displaying a distinct temporal and spatial expression pattern (139)(140)(141)(142)(143)(144)(145)(146)(150)(151)(152). The gamma-subunit is a small (8-14 kD) hydrophobic peptide whose function is c urrently under investigation (146,148,150).…”

Advances in Na+,K+‐ATPase studies: from protein to gene and back to protein

“…Only one sequence was found in the kidney of sheep [15] and pigs [16,19]. However, further investigations of chromosomal genes for the a-subunit of human Na+,K+-ATPase [28,29], as well as of the screening of cDNA library from rat brain [30] have led to the discovery of the gene family. At present, probably, about seven sequences, highly homologous to the gene for the a-subunit, were cloned in the human genome [29,31].…”

“…At present, probably, about seven sequences, highly homologous to the gene for the a-subunit, were cloned in the human genome [29,31]. Out of these genes, three correspond to the three mRNAs (aI, ~~11, aIII), found in rat brain which code for three isoforms of the enzyme a-subunit [30]. One of the genes appeared to be the gene encoding H+,K+-ATPase [29,32].…”

Family of human Na+,K+‐ATPase genes Structure of the putative regulatory region of the α+‐gene

“…Na+,K+-ATPase of animal cells is an integral membrane protein, containing a catalytic asubunit and a P-subunit of unknown function (review [ 11). As demonstrated previously, there are two distinct isoforms of the a-subunit, called LY and a', and their localization is tissue-specific (review [2]).…”