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CBP70, a glycosylated nuclear lectin
C Rousseau1, M Felin, M A Doyennette-Moyne
1Laboratoire des Glycoprotéines et des Lectines Nucléaires, Hopital St. Louis, Paris, France.
Journal of Cellular Biochemistry
|September 1, 1997
Summary
Nuclear and cytoplasmic CBP70, a glucose-binding lectin, share a common backbone but exhibit distinct glycosylation patterns. This difference in N- and O-glycosylation likely influences their cellular targeting and function.
Area of Science:
- Molecular Biology
- Glycobiology
- Cell Biology
Background:
- CBP70 is a lectin initially isolated from HL60 cell nuclei, known to bind glucose and N-acetylglucosamine.
- Both nuclear and cytoplasmic forms of CBP70 have been described, with a previously characterized 82 kDa nuclear ligand.
- Previous research identified CBP70 as a glucose-binding lectin with higher affinity for N-acetylglucosamine.
Purpose of the Study:
- To determine if nuclear and cytoplasmic CBP70 are the same protein by analyzing their polypeptide backbone.
- To investigate the post-translational modifications, specifically glycosylation, of both nuclear and cytoplasmic CBP70.
- To compare the glycosylation patterns of nuclear and cytoplasmic CBP70 to understand potential functional differences.
Main Methods:
- Pronase digestion and trifluoromethanesulphonic acid (TFMS) procedures were used to analyze the protein backbone.
- Glycosylation analysis involved beta-elimination, hydrazinolysis, peptide-N-glycosydase F (PNGase F), and TFMS reactions.
- Affinity chromatography on immobilized lectins (RCA-I, PNA, GNA, WGA) and lectin-blotting (SNA, MAA, Lotus, succinylated-WGA, PVA) were employed.
Main Results:
- Both nuclear and cytoplasmic CBP70 share a common 23 kDa polypeptide backbone, suggesting they are the same protein.
- Both forms are N- and O-glycosylated, but exhibit distinct glycosylation patterns.
- Specific sugar moieties identified include terminal beta Gal, Gal beta 1-3 GalNAc, Man alpha 1-3 Man, and sialic acid linkages; nuclear CBP70 uniquely possesses terminal GlcNAc and alpha-L-fucose residues.
Conclusions:
- Nuclear and cytoplasmic CBP70 are likely the same protein with differing post-translational glycosylation.
- The distinct glycosylation patterns between nuclear and cytoplasmic CBP70 may serve as a signal for cellular targeting.
- Understanding these glycosylation differences is crucial for future recombinant protein production and elucidating CBP70 function.