cDNA cloning of Na⁺, K⁺-ATPase α-subunit from embryos of the sea urchin, Hemicentrotus pulcherrimus

Na⁺, K⁺-ATPase α-subunit cDNA of the sea urchin, Hemicentrotus pulcherrimus, was obtained by twice screening prism and gastrula λgt10 cDNA libraries using an oligonucleotide probe derived from a mostly conserved region, FSBA (5′-p-(fluorosulfonyl)-benzoyladenosine) binding site of cation transport ATPases. The 5′-end of the non-coding region was determined by primer extension and the region was amplified by 5′-RACE method. The sea urchin α-subunit cDNA consists of 4401 nucleotides and encodes 1038 amino acid residues (MW, 114 kDa). The predicted primary structure, except N-terminal region, has similar degree of high homology to various metazoan Na⁺, K⁺-ATPase α-subunits. Alignment of amino acid sequence and a hydropathy profile also predicts eight putative transmembrane segments at least. The phylogenetic tree suspected from alignment of amino acid sequences of 21 species suggests that sea urchin and vertebrate Na⁺, K⁺-ATPase α-subunits seem to have evolved from a common origin, before vertebrate α-subunit divided into three isoforms.