title: The Beta-subunit of the rabbit H,K-ATPase:a glycoprotein with all terminal lactosamine units capped with alpha-linked galactose residues.
abstract: The beta-subunit of the gastric H,K-ATPase is the most abundant glycoprotein in the tubulovesicular compartment of the acid-secreting parietal cells. The oligosaccharides of the beta-subunit have been shown to contain fucose, N-acetylglucosamine, mannose, galactose, and N-acetylgalactosamine. Previous studies have shown that the rabbit beta-subunit is devoid of N-acetylneuraminic acid. Here we report the structural features of the N-linked oligosaccharides of the beta-subunit from rabbit H,K-ATPase. We used glycosidase digestions and analysis by high-pH anion-exchange chromatography with pulsed amperometric detection and matrix-assisted laser desorption/ionization mass spectrometry to analyze the peptide-N4-(N-acetyl-beta-D-glucosaminyl)asparagine amidase (PNGase F)- and endo-beta-N-acetylglucosaminidase H (Endo H)-released oligosaccharides. The studies showed that the oligosaccharides of the beta-subunit are a mixture of both oligomannosidic and lactosamine-type structures. The high-mannose structures were identified as Man5Man8GlcNAc2 species. A striking finding was that all the branches of the lactosamine-type structures were terminated with Galalpha-->Galbeta-->GlcNAc extensions. All of the lactosamine-type structures were found to be core fucosylated and some of them contained one to three lactosamine repeats. We propose that a part of the adaptation of the gastric beta-subunit to the acidic environment of the stomach is through providing acid-stable terminal residues on the oligosaccharides.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.
authors.forename: K
authors.initials: K
authors.lastname: Tyagarajan
authors.forename: R R
authors.initials: RR
authors.lastname: Townsend
authors.forename: J G
authors.initials: JG
authors.lastname: Forte
mesh_terms: D000581:Amidohydrolases / Q000378:metabolism; D000606:Amino Sugars / Q000032:analysis*; D000818:Animals; D002240:Carbohydrate Sequence; D002852:Chromatography, Ion Exchange; D005690:Galactose / Q000032:analysis*; D006023:Glycoproteins / Q000737:chemistry*; D006026:Glycoside Hydrolases / Q000378:metabolism; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry*; D007536:Isomerism; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry*; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D011817:Rabbits; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000606:Amino Sugars; D006023:Glycoproteins; D009844:Oligosaccharides; C032233:lactosamine; D006026:Glycoside Hydrolases; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D017506:H(+)-K(+)-Exchanging ATPase; D005690:Galactose