Mouse embryonic development and tumor cell growth under the influence of recombinant trichosanthin (a ribosome inactivating protein) and its muteins

Trichosanthin, a ribosome inactivating protein, is known to possess embryotoxic and antiproliferative activities. In the present study recombinant trichosanthin and its muteins produced by site-directed mutagenesis were tested for these activities using whole embryo culture and cell culture. The results revealed that when Glu 160 in trichosanthin was mutated to alanine or aspartate, the two aforementioned activities underwent a substantial decrease. However, the former mutein had a higher potency than the latter mutein. When both Glu 160 and Glu 189 were mutated, the resultant mutant possessed very low antiproliferative and yet considerable embryotoxic activity, indicating the contribution from other amino acids in stabilizing the transition state complex of trichosanthin. (C) 1996 Wiley-Liss, Inc.