Design, synthesis, and immunochemical characterization of a chimeric glycopeptide corresponding to the Shigella flexneri Y O-polysaccharide and its peptide mimic MDWNMHAA.
Two glycopeptide chimeras corresponding to the Shigella flexneri Y O-polysaccharide and its peptide mimic were designed in an attempt to improve the binding affinity by increasing the entropy of binding relative to the original octapeptide mimic of the O-polysaccharide. The design was based on the X-ray crystal structures of a monoclonal antibody SYA/J6 in complex with its cognate ligands, a pentasaccharide corresponding to the S. flexneri Y O-polysaccharide and the octapeptide mimic, MDWNMHAA. Both chimeric molecules consist of a rhamnose trisaccharide linked through an alpha- or beta-thioglycosidic linkage to a MDW moiety in which the W unit has been modified. We predicted that omission of the NMHAA moiety would obviate the bound water molecules that provided complementarity with the antibody-combining site, and the conformational restriction resulting from imposition of an alpha-turn at the C-terminus of the peptide. The glycopeptides were then docked into the active site of SYA/J6 using the program autodock 3.0, and the structures were optimized. The best models obtained in each case showed that the chimeric molecules, with either an alpha- or beta-thioglycosidic linkage, might be reasonable surrogate ligands for the antibody. We report here the synthesis of the alpha-glycopeptide employing solution and solid-phase strategies. Immunochemical characterization indicated that the alpha-glycopeptide unfortunately did not inhibit binding of SYA/J6 to the S. flexneri Y lipopolysaccharide.
Hossany
B Rehana
BR
Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6.
Johnston
Blair D
BD
Wen
Xin
X
Borrelli
Silvia
S
Yuan
Yue
Y
Johnson
Margaret A
MA
Pinto
B Mario
BM
D002240:Carbohydrate Sequence; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004797:Enzyme-Linked Immunosorbent Assay; D006020:Glycopeptides / Q000138:chemical synthesis* / Q000737:chemistry* / Q000276:immunology; D007150:Immunohistochemistry / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000276:immunology*; D012763:Shigella flexneri / Q000378:metabolism*
D006020:Glycopeptides; D011135:Polysaccharides, Bacterial