title: Conformation-independent binding of monoglucosylated ribonuclease B to calnexin.
abstract: Calnexin is a membrane protein of the endoplasmic reticulum that associates transiently with newly synthesized N-linked glycoproteins in vivo. Using defined components, the binding of ribonuclease B (RNase B) Man7-Man9 glycoforms to the luminal domain of calnexin was observed in vitro only if RNase B was monoglucosylated. Binding was independent of the conformation of the glycoprotein. Calnexin protected monoglucosylated RNase B from the action of glucosidase II and PNGase F but not from that of Endo H, which completely released the protein from calnexin. These observations directly demonstrate that calnexin can act exclusively as a lectin.
authors.affiliation: Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Zapun
authors.forename: S M
authors.initials: SM
authors.lastname: Petrescu
authors.forename: P M
authors.initials: PM
authors.lastname: Rudd
authors.forename: R A
authors.initials: RA
authors.lastname: Dwek
authors.forename: D Y
authors.initials: DY
authors.lastname: Thomas
authors.forename: J J
authors.initials: JJ
authors.lastname: Bergeron
mesh_terms: D000581:Amidohydrolases; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D037281:Calnexin; D002417:Cattle; D004285:Dogs; D005964:Glucosyltransferases; D006031:Glycosylation; D006596:Hexosaminidases; D007535:Isomerases; D008358:Mannose / Q000737:chemistry; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008956:Models, Chemical; D009844:Oligosaccharides / Q000378:metabolism; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D011485:Protein Binding; D011487:Protein Conformation; D019704:Protein Disulfide-Isomerases; D017510:Protein Folding; D051381:Rats; D012260:Ribonucleases / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D014532:Uridine Diphosphate Glucose / Q000378:metabolism; D000520:alpha-Glucosidases
chemical_list: D002135:Calcium-Binding Proteins; D009844:Oligosaccharides; D037281:Calnexin; D005964:Glucosyltransferases; D012260:Ribonucleases; C029600:ribonuclease B; C034251:4-nitrophenyl-alpha-glucosidase; D006596:Hexosaminidases; D000520:alpha-Glucosidases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D007535:Isomerases; D019704:Protein Disulfide-Isomerases; D008358:Mannose; D014532:Uridine Diphosphate Glucose