BINDING OF MODIFIED FRAGMENTS OF THE SHIGELLA-DYSENTERIAE TYPE-1 O-SPECIFIC POLYSACCHARIDE TO MONOCLONAL IGM-3707 E9 AND DOCKING OF THE IMMUNODETERMINANT TO ITS MODELED FV

The O-specific polysaccharide (O-SP) of Shigella dysenteriae type 1 ha s been shown by others to have the structure --> 3)-alpha-L-Rhap-(1 -- > 3)-alpha-L-Rhap-(1 --> 2)-alpha-D-Galp-(1 --> 3)-alpha-D-GlcpNAc-(1 -->. We have shown in the past that IgM 3707 E9, an anti S. dysenteria e type 1 O-SP monoclonal antibody, binds specifically to the -alpha-L- Rhap-(1 --> 2)-alpha-D-Galp- determinant of the polysaccharide. In thi s report we show that determinant to have hydrogen bonds, necessary fo r binding to the antibody, involving positions 3, 4 and 6 of the galac topyranosyl residue. The hydroxyl groups of the rhamno-pyranosyl moiet y of the immunodeterminant appear not to partake in hydrogen-bond inte ractions with the antibody. A model is presented of the Fv of IgM 3707 E9 based on our previously established cDNA-sequence and two known, h ighly homologous immunoglobulin crystal structures. The methyl glycosi de of the immunodeterminant alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-D- galactopyranose is docked to the combining area of the Fv. (C) 1998 El sevier Science Ltd. All rights reserved.