Characterization of a beta subunit of the gastric H+/K(+)-transporting ATPase.
The catalytic subunit of the H+/K(+)-transporting ATPase (EC 3.6.1.3) has 62% identity to the alpha, or catalytic subunit, of the Na+/K(+)-transporting ATPase (EC 3.6.1.37); however, a homologous beta subunit was unknown until recently. Removal of the carbohydrate from purified hog H+/K(+)ATPase vesicles reveals a 35-kDa peptide that, when fragmented with protease V8, gives sequences homologous to both beta 1 and beta 2 subunits of the Na+/K(+)-ATPase. cDNA clones for a beta subunit of the gastric H+/K(+)-ATPase were isolated from a rabbit stomach cDNA library by using degenerate 17-mer oligonucleotide probes made to the protease V8-treated peptides. An open reading frame (54-926) encodes a predicted 291-amino acid peptide with Mr = 33,320, which exhibits 31% and 44% homologies to the Na+/K+)-ATPase beta 1 and Na+/K(+)-ATPase beta 2 proteins, respectively. A Kyte-Doolittle hydropathy plot predicts a single N-terminal transmembrane domain with a small hydrophobic region near the C terminus. The presumed extracytosolic domain contains seven potential N-linked glycosylation sites and six out of nine cysteines. Northern (RNA) blot analysis of stomach RNA with the rabbit H+/K(+)-ATPase beta probe identifies a single mRNA of 1.3-1.5 kilobases, similar in concentration to the alpha subunit mRNA. The presence of a defined gastric H+/K(+)-ATPase beta subunit extends the homology between H+/K(+)-ATPase and the Na+/K(+)-ATPase subclass of phosphoenzyme transport ATPases and distinguishes them from the monomeric Ca2+ and proton pump subclasses.
Reuben
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MA
Center for Ulcer Research and Education, Wadsworth Veterans Administration Hospital, Los Angeles, CA.
Lasater
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LS
Sachs
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D000251:Adenosine Triphosphatases / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D015723:Gene Library; D017506:H(+)-K(+)-Exchanging ATPase; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010455:Peptides / Q000138:chemical synthesis; D011487:Protein Conformation; D011817:Rabbits; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D012984:Software; D013270:Stomach / Q000201:enzymology*; D013552:Swine
D046911:Macromolecular Substances; D015345:Oligonucleotide Probes; D010455:Peptides; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase