Specific binding of phenolic glycolipid antigens from Mycobacterium bovis BCG with antibodies.
Ключови думи
Резюме
We studied the molecular binding specificity of two rabbit polyclonal sera generated against phenolic glycolipid antigens namely PheG1 B and PheG1 B-3 from Mycobacterium bovis BCG. PheG1 B is the well-known mycoside B (2-O-Me-alpha-L-Rhap 1----aglycone), while PheG1 B-3 is a recently found glycolipid (alpha-L-Rhap-(1----3)-2-O-Me-alpha-L-Rhap 1----aglycone). The interaction specificity was mainly explained in terms of the cavity volume of the antibodies paratope. The anti-PheG1 B antibodies paratope fits the 2-O-Me-alpha-L-Rhap ligand, while that of anti-PheG1 B-3 binds the disaccharide moiety of PheG1 B-3, and, with a higher affinity, the monosaccharidic unit localized at the non-reducing end. The B-3 antigen affinity is higher than that of antigen B for their homologous antibodies. This can be explained by the fact that the antibodies against phenolic glycolipid B-3 bind optimally to two sequential glycosyl residues suggesting the presence of two subsites. The immunoglobulin subsite with the major affinity binds the monosaccharidic unit localized at the non-reducing end.