NMR studies of the antibody-bound conformation of a carbohydrate-mimetic peptide |
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Authors: | Johnson Margaret A Rotondo Archimede Pinto B Mario |
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Affiliation: | Departments of Chemistry and of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6. |
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Abstract: | Transferred nuclear Overhauser enhancement (TRNOE) experiments have been performed at 800 MHz to investigate the bound conformation of the hexapeptide DRPVPY, a functional molecular mimic of the group A Streptococcus cell-wall polysaccharide. The hexapeptide binds to the monoclonal antibody SA-3, mimicking the branched trisaccharide repeating unit, L-Rha-alpha-(1 --> 2)-(D-GlcNAc-beta-(1 --> 3))-alpha-L-Rha (Rha, rhamnose; GlcNAc, N-acetylglucosamine). The peptide adopts a tight turn conformation with close contacts between the side chains of valine and tyrosine. Relaxation network editing experiments (QUIET-NOESY) were used to confirm the validity of the observed contacts and to evaluate the presence of spin diffusion pathways. Saturation transfer difference (STD-NMR) experiments with selective saturation of protein resonances revealed enhancements of many of the peptide resonances due to close contacts between the peptide and the protein within the antibody combining site. |
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