THE VARIABLE DOMAIN GLYCOSYLATION IN A MONOCLONAL-ANTIBODY SPECIFIC TO GNRH MODULATES ANTIGEN-BINDING

Functionally important glycosylation has been identified in the antige n binding domain of an anti-GnRH monoclonal antibody, Presence of mann ose and sialic acid residues is revealed from con A immunoblots and po sitive staining with a sialic acid detection kit, respectively. Desial ylation of the antibody reduces GnRH binding, suggesting the role of t erminal sialic acid residues in modulating antigen binding, The crysta l structure of the Fab fragment shows electron density adjacent to the antigen binding site which may be attributed to the covalently attach ed carbohydrate moiety, Thus, the presence of sialic acid containing m annose-rich carbohydrate moiety near the antigen binding site of a mon oclonal antibody Fab fragment is relevant for defining antibody specif icity. (C) 1997 Academic Press.