CDNA CLONING OF NA-ATPASE ALPHA-SUBUNIT FROM EMBRYOS OF THE SEA-URCHIN, HEMICENTROTUS-PULCHERRIMUS(,K+)

Na+, K+-ATPase alpha-subunit cDNA of the sea urchin, Hemicentrotus pul cherrimus, was obtained by twice screening prism and gastrula lambda g t10 cDNA libraries using an oligonucleotide probe derived from a mostl y conserved region, FSBA (5'-p-(fluorosulfonyl)-benzoyladenosine) bind ing site of cation transport ATPases. The 5'-end of the non-coding reg ion was determined by primer extension and the region was amplified by 5'-RACE method. The sea urchin alpha-subunit cDNA consists of 4401 nu cleotides and encodes 1038 amino acid residues (MW, 114 kDa). The pred icted primary structure, except N-terminal region, has similar degree of high homology to various metazoan Nac, K+-ATPase alpha-subunits. Al ignment 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 suggest s that sea urchin and vertebrate Na+, K+-ATPase alpha-subunits seem to have evolved from a common origin, before vertebrate alpha-subunit di vided into three isoforms.