Structural characterization of gelonin: evidence for separate antigenic and cytotoxic domains.

The N-terminal sequence of the three isoforms of gelonin is identical. Cyanogen bromide cleavage of gelonin produced fragments of Mr 17,000, 13,000, 11,000 and 7,000. The apparent Mr 17,000 component was identified as the N-terminal fragment and represents the major antigenic domain of the protein as it reacted with antibody to the native protein but this fragment did not inhibit protein synthesis in the in vitro translation assay. Our data may suggest possibilities for separation of antigenic and catalytic domains of this ribosome inactivating protein.