TAILIEUCHUNG - Báo cáo khoa học: Total chemical synthesis and NMR characterization of the glycopeptide tx5a, a heavily post-translationally modified conotoxin, reveals that the glycan structure is a-D-Gal-(1fi3)-a-D-GalNAc

The 13-amino acid glycopeptide tx5a (Gla-Cys-Cys-Gla-Asp-Gly-Trp*-Cys-Cys-Thr*-Ala-Ala-Hyp-OH, where Trp*¼6-bromotryptophan and Thr*¼Gal-GalNAc-threonine), isolated fromConus textile, causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationallymodified residues: four cysteine residues, twoc-carboxyglutamic acid residues, and one residue each of 6-bromotryptophan, 4-trans-hydroxyproline and glycosylated threonine. | Eur. J. Biochem. 271 4939-4949 2004 FEBS 2004 doi Total chemical synthesis and NMR characterization of the glycopeptide tx5a a heavily post-translationally modified conotoxin reveals that the glycan structure is a-D-Gal- 1fi3 -a-D-GalNAc James Kana1 William Low1 Thomas Norbera3 Jill Meisenhelder2 Karin Hansson4 Johan Stenflo4 Guo-Ping Zhou5 6 Julita Imperial7 Baldomero M. Olivera7 Alan C. Rigby5 6 and A. Grey Craig1 1The Clayton Foundation Laboratories for Peptide Biology and 2Laboratory for Molecular and Cell Biology The Salk Institute La Jolla CA USA 3Department of Chemistry Swedish University of Agricultural Sciences Uppsala Sweden 4Department of Clinical Chemistry University of Lund Malmo General Hospital Malmo Sweden 5Center for Hemostasis and Thrombosis Research Beth Israel Deaconess Medical Center Harvard Medical School Boston MA USA 6Marine Biological Laboratory Woods Hole MA USA 1 Department of Biology University of Utah Salt Lake City UT USA The 13-amino acid glycopeptide tx5a Gla-Cys-Cys-Gla-Asp-Gly-Trp -Cys-Cys-Thr -Ala-Ala-Hyp-OH where Trp 6-bromotryptophan and Thr Gal-GalNAc-threonine isolated from Conus textile causes hyperactivity and spasticity when injected intracerebral ventricularly into mice. It contains nine post-translationally modified residues four cysteine residues two y-carboxyglutamic acid residues and one residue each of 6-bromotryptophan 4-trans-hydroxyproline and glycosylated threonine. The chemical nature of each of these has been determined with the exception of the glycan linkage pattern on threonine and the stereochemistry of the 6-bromotryptophan residue. Previous investigations have demonstrated that tx5a contains a disaccharide composed of N-acetylgalactosamine GalNAc and galactose Gal but the interresidue linkage was not characterized. We hypothesized that tx5a contained the T-antigen P-D-Gal- 1fi3 -a-D-GalNAc one of the most common O-linked glycan structures identified previously in another .

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