THE ANTIGENIC SITES OF TRICHOSANTHIN, A RIBOSOME-INACTIVATING PROTEINWITH MULTIPLE PHARMACOLOGICAL PROPERTIES

Trichosanthin (TCS) fragments were produced by Tn1000 deletion mutagen esis and by cyanogen bromide (CNBr) cleavage and their immunoreactivit y was examined by incubating with various antibodies. Twelve C-termina lly truncated TCS variants were successfully synthesized under the con trol of a T7 RNA driven promoter. The smallest antigenic fragment mapp ed corresponded to the N-terminal 20 amino acids (aa). Six CNBr fragme nts of TCS were created and identified by electrospray mass spectromet ry and N-terminal sequencing, Three antigenic fragments corresponding to aa 1-72, 101-152 and 153-246, respectively were mapped. Fragments c orresponding to aa 1-72 and 153-246 were immunoreactive to the same mo noclonal antibody showing they are components of a discontinuous epito pe. On the other hand, the fragment containing aa 73-100 was not detec ted by any of the antibodies used.