Antigenic determinant of trichosanthin peptide fragments

Purified plant protein, Trichosanthin (TCS), was partially digested with chymotrypsin to produce peptide fragments. Two large fragments, I and II, have been isolated and identified as C-terminal peptides located at sequence positions between 79-234 and 107-234. Their molecular weights determined by electrophoretic mobility on SDS gel were 16,000 and 14,000 daltons. Studies using fluorescence quenching measurements by titrating anti-TCS Fab with TCS and fragment I and II showed that four epitopes were present in intact TCS and one each epitope in fragment I and II. One of the epitopes is therefore located between sequence positions 107 and 234.