RIBOSOME-INACTIVATING PROTEINS (RIPS) OF WILD OREGON CUCUMBER (MARAH OREGANUS)

Two type 1 RIPs, designated as MOR-I and MOR-II, have been isolated fr om Marah oreganus (manroot) seed extract. They are similar but not ide ntical to trichosanthin, a type 1 RIP in the same family. MOR-I and MO R-II are monomeric proteins with molecular weights of 27989.0 and 2763 2.8 respectively and have pi values greater than 8.8. MOR-I and MOR-II inhibit cell-free protein synthesis with IC(50)s of 0.063 and 0.071 n M, respectively, and are relatively stable with respect to temperature and pH variations. They share a conserved N-terminal amino acid seque nce (D-SF-LS) and cross-react with goat anti-trichosanthin polyclonal serum.