title: Covalent structure of bovine brain calreticulin.
abstract: The covalent structure of bovine brain calreticulin, a major Ca(2+)-binding protein in the lumen of the endoplasmic reticulum, was determined by analysis of the purified protein. The protein consisted of 400 amino acids, with an N-linked oligosaccharide attached to the polypeptide chain. The polypeptide sequence determined was compatible with the sequence of calreticulin deduced from cDNA of different sources, with a number of differences presumably due to species-specific amino acid substitutions. The protein retained the C-terminal tetrapeptide, KDEL, involved in retention of proteins resident in the endoplasmic reticulum, whereas the N-terminal signal peptide predicted from the cDNA sequence had been removed in the purified protein. The bovine brain protein contained a high-mannose type of oligosaccharide attached to Asn162, which is typical of resident endoplasmic reticulum proteins. The carbohydrate moiety was heterogeneous and had the composition GlcNAc2Man4-9, of which GlcNAc2Man5 was the most abundant in the bovine brain preparation. Glycosylation of calreticulin, however, appeared to be a species-specific modification, as Asn162 is replaced by Asp in the sequences already determined for a number of species. Analysis of the purified protein also identified an intramolecular disulphide bridge between Cys120 and Cys146.
authors.affiliation: Department of Chemistry, Faculty of Science, Tokyo Metropolitan University, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Matsuoka
authors.forename: K
authors.initials: K
authors.lastname: Seta
authors.forename: Y
authors.initials: Y
authors.lastname: Yamakawa
authors.forename: T
authors.initials: T
authors.lastname: Okuyama
authors.forename: T
authors.initials: T
authors.lastname: Shinoda
authors.forename: T
authors.initials: T
authors.lastname: Isobe
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry; D002135:Calcium-Binding Proteins / Q000737:chemistry*; D037282:Calreticulin; D002240:Carbohydrate Sequence; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004220:Disulfides / Q000032:analysis; D015180:Electrophoresis, Gel, Two-Dimensional; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000032:analysis; D010449:Peptide Mapping; D011487:Protein Conformation; D012261:Ribonucleoproteins / Q000737:chemistry*
chemical_list: D002135:Calcium-Binding Proteins; D037282:Calreticulin; D004220:Disulfides; D009844:Oligosaccharides; D012261:Ribonucleoproteins