Linked Life Data

9521669

Source:http://linkedlifedata.com/resource/pubmed/id/9521669

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
10
pubmed:dateCreated
1998-4-21
pubmed:abstractText
Calnexin and calreticulin are homologous molecular chaperones of the endoplasmic reticulum. Their binding to newly synthesized glycoproteins is mediated, at least in part, by a lectin site that recognizes the early N-linked oligosaccharide processing intermediate, Glc1Man9GlcNAc2. We compared the oligosaccharide binding specificities of calnexin and calreticulin in an effort to determine the basis for reported differences in their association with various glycoproteins. Using mono-, di-, and oligosaccharides to inhibit the binding of Glc1Man9GlcNAc2 to calreticulin and to a truncated, soluble form of calnexin, we show that the entire Glc alpha 1-3Man alpha 1-2Man alpha 1-2Man structure, extending from the alpha 1-3 branch point of the oligosaccharide core, is recognized by both proteins. Furthermore, analysis of the binding of monoglucosylated oligosaccharides containing progressively fewer mannose residues suggests that for both proteins the alpha 1-6 mannose branch point of the oligosaccharide core is also essential for recognition. Consistent with their essentially identical substrate specificities, calnexin and calreticulin exhibited the same relative affinities when competing for binding to the Glc1Man9GlcNAc2 oligosaccharide. Thus, differential glycoprotein binding cannot be attributed to differences in the lectin specificities or binding affinities of calnexin and calreticulin. We also examined the effects of ATP, calcium, and disulfide reduction on the lectin properties of calnexin and calreticulin. Whereas oligosaccharide binding was only slightly enhanced for both proteins in the presence of high concentrations of a number of adenosine nucleotides, removal of bound calcium abrogated oligosaccharide binding, an effect that was largely reversible upon readdition of calcium. Disulfide reduction had no effect on oligosaccharide binding by calnexin, but binding by calreticulin was inhibited by 70%. Finally, deletion mutagenesis of calnexin and calreticulin identified a central proline-rich region characterized by two tandem repeat motifs as a segment capable of binding oligosaccharide. This segment bears no sequence homology to the carbohydrate recognition domains of other lectins.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
10
pubmed:volume
37
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3480-90
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:9521669-Adenosine Triphosphate, pubmed-meshheading:9521669-Amino Acid Sequence, pubmed-meshheading:9521669-Animals, pubmed-meshheading:9521669-Binding Sites, pubmed-meshheading:9521669-Calcium-Binding Proteins, pubmed-meshheading:9521669-Calnexin, pubmed-meshheading:9521669-Calreticulin, pubmed-meshheading:9521669-Carbohydrate Sequence, pubmed-meshheading:9521669-Cell Line, pubmed-meshheading:9521669-Cricetinae, pubmed-meshheading:9521669-Dithiothreitol, pubmed-meshheading:9521669-Egtazic Acid, pubmed-meshheading:9521669-Endoplasmic Reticulum, pubmed-meshheading:9521669-Mice, pubmed-meshheading:9521669-Molecular Chaperones, pubmed-meshheading:9521669-Molecular Sequence Data, pubmed-meshheading:9521669-Oligosaccharides, pubmed-meshheading:9521669-Peptide Mapping, pubmed-meshheading:9521669-Protein Binding, pubmed-meshheading:9521669-Recombinant Fusion Proteins, pubmed-meshheading:9521669-Ribonucleoproteins, pubmed-meshheading:9521669-Sequence Deletion
pubmed:year
1998
pubmed:articleTitle
Oligosaccharide binding characteristics of the molecular chaperones calnexin and calreticulin.
pubmed:affiliation
Department of Biochemistry, University of Toronto, Ontario, Canada.
pubmed:publicationType
Journal Article, In Vitro, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't