Cloning, sequencing, and expression of a human brain ecto-apyrase related to both the ecto-ATPases and CD39 ecto-apyrases1.
An extracellular ATPase (E-type ATPase) clone was isolated from a human brain cDNA library and sequenced. The transcript shows similarity to the previously published chicken smooth muscle and rat brain ecto-ATPase cDNAs, human CD39L1 cDNA (putative human ecto-ATPase), and mammalian CD39 (lymphoid cell activation antigen, ecto-apyrase, ATPDase, ATP-diphosphohydrolase) cDNAs. The full-length human brain cDNA encodes a 529 amino acid glycoprotein with a putative membrane spanning region near each terminus, with the majority of the protein found extracellularly. Expression of this clone in mammalian COS-1 cells yielded NaN3-sensitive ATPase and ADPase activity detectable both on intact cells and cell membrane preparations. The nucleotide hydrolysis ratio of the expressed protein is approx. 2.75:1 (ATPase:ADPase activity), classifying it as an ecto-apyrase. However, this hydrolysis ratio is intermediate between that observed for the ecto-ATPases and the CD39 ecto-apyrases (L. Plesner, Int. Rev. Cytol. 158 (1995) 141-214). Quantitative analyses of amino acid identities and similarities between this ecto-apyrase and other vertebrate E-type ATPases suggest that this human brain enzyme is nearly equally related to the ecto-ATPases and the CD39s, and phylogenetic analysis suggests that it could be an ancestral enzyme from which both ecto-ATPases and CD39 ecto-apyrases are derived.
Smith
T M
TM
Department of Pharmacology and Cell Biophysics, College of Medicine, University of Cincinnati, 231 Bethesda Avenue, Cincinnati, OH 45267-0575, USA.
Kirley
T L
TL
D000251:Adenosine Triphosphatases / Q000235:genetics; D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000235:genetics; D001081:Apyrase / Q000096:biosynthesis / Q000145:classification / Q000235:genetics*; D001483:Base Sequence; D001921:Brain / Q000201:enzymology*; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D015723:Gene Library; D006801:Humans; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D015703:Antigens, CD; D018076:DNA, Complementary; D011994:Recombinant Proteins; D000251:Adenosine Triphosphatases; C027201:ectoATPase; D001081:Apyrase; C067869:CD39 antigen