Effect of solution conformation on antibody recognition of a protein core epitope from gastrointestinal mucin (MUC2)

Antibody recognition of the tandem repeat unit of MUC2 glycoprotein was inv estigated, To clarify the role of secondary structure, the immunoreactivity and conformation of overlapping and truncated peptides mere investigated. For this several MUC2 peptides have been synthesized and their secondary st ructure has been analyzed by circular dichroism and Fourier transform infra red spectroscopical methods. For the binding studies a MUC2 mucin protein c ore-specific monoclonal antibody was used in competition BIA experiments. T he minimal size peptide functioning as epitope was peptide (18)PTGTQ(22). W ithin the immunodominant (13)TPTPTGTQTPTT(26) region we found that all pept ides recognized by the 996 monoclonal antibody adopted beta-turns secondary structure. Peptides (15)TPTPTGTQ(22) and (16)PTPTGTQ(22), containing the m ost prominent beta-turn(s), had the strongest immunoreactivity. It was also observed that peptides with Pro on their N-termini ((16)PTPTGTQ(22), (18)P TGTQ(22)) adopt a different type of beta-turn in TFE than peptides with Thr at their N-terminal. Based on the antibody binding, molecular dynamics cal culations, and secondary structure analysis, we propose a model for the epi tope structure of the MUC2 mucin tandem repeat. (C) 1999 Academic Press.