Multiple carbohydrate moieties on the Na+/H+ exchanger.
Affinity-purified antibodies against the C-terminal region of the Na+/H+ exchanger (NHE-1) were used to analyse the carbohydrate moiety of the protein. The Na+/H+ exchanger in human placental brush-border membranes has an apparent molecular mass of 105 kDa. Incubation of intact or detergent-solubilized membranes with glycopeptidase F removed the carbohydrate moiety and increased the apparent mobility of the exchanger. Digestion with endoglycosidase-F caused a similar change in mobility, but endoglycosidase-H had no effect, suggesting that the placental Na+/H+ exchanger is a glycoprotein of the biantennary complex type. Removal of the carbohydrate moiety with glycopeptidase F had no effect on the ability of the protein to promote the exchange of Na+ for H+, and had no detectable effect on the sensitivity of the exchanger to trypsin. Limited digestion with glycopeptidase F and neuraminidase indicated the presence of two intermediate forms between the fully glycosylated and the deglycosylated protein. This suggests the presence of at least two, and possibly three, N-linked carbohydrate moieties.
Department of Pediatrics, University of Alberta, Edmonton, Canada.
R S
RS
Haworth
O
O
Fröhlich
L
L
Fliegel
D000581:Amidohydrolases / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D050260:Carbohydrate Metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000187:drug effects; D004586:Electrophoresis; D006023:Glycoproteins / Q000737:chemistry* / Q000187:drug effects; D006801:Humans; D008871:Microvilli / Q000737:chemistry*; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D010920:Placenta / Q000737:chemistry* / Q000648:ultrastructure; D017923:Sodium-Hydrogen Exchangers; D014357:Trypsin / Q000494:pharmacology
D002352:Carrier Proteins; D006023:Glycoproteins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D014357:Trypsin; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase