Isolation of antigenically reactive peptide fragments and localization of antigenic regions of alpha-bungarotoxin.

alpha-Bungarotoxin was digested with acid protease A and the resulting peptide fragments were isolated by reverse-phase HPLC. The antigenic activity of the peptide fragments were examined by competitive solid phase radioimmunoassay and the probably sequences were assigned. The two antigenic regions are likely located around the residues 34-41 and 68-74 of alpha-bungarotoxin, and the other two may be within the residues 3-26 and 45-67, respectively. Radioimmunoassay revealed a maximum number of four antigenic determinants of alpha-bungarotoxin that can simultaneously be occupied by antibody.