Determination of Antigenic Epitopes Recognized by Four Monoclonal Antibodies to Glutathione S-Transferase п (GST-п)

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Abstract
Four independent antibodies (6A, 5F, 2H and 2F) to Glutathione S-transferase п (GST-п) were selected to characterize their epitopes. Amino acid analysis of 5.6 K and 7.4 K tryptic peptides appeared to suggest that the epitope recognized by antibodies 2H and 2F is located in the N-terminal 44 peptides of GST-п, and that of 6A and 5F is located in the C-terminal 69 peptides. Reactivities of antibodies 6A and 5F with two synthetic peptides indicated that 6A recognized an epitope in the C-terminal hydrophilic fragment 176Leu-209Gln, and could be distinguished from 5F which recognized an epitope in the 141Thr-176Leu hydrophobic fragment. The differential immuno-reactivity of antibodies 6A and 5F with GST-п itself, was characterized by the particularly high reactivity of 6A and almost no reactivity of 5F with the natural conformation of GST-п in solution. This may be explained by differences in the hydropathic natures of their epitopes. The 6A antibody was useful for immunodetection of GST-п in circulation, while 5F was found to be most suitable for histochemical staining of tumor tissue.