The three-dimensional structure of trichosanthin at 2.7A resolution has been improved further, by refitting one of the C-terminal tails, adjusting 16 residues in the molecular surface regions, discarding some water molecules with high B values, and adjusting weights during the further refinement. The R-factor has been reduced to 18.5% and the r.m.s deviations from ideal geometry are also improved. The structures of the two molecules in the monoclinic asymmetric unit and the only molecule in the orthorhombic asymmetric unit are compared with one another. The main-chain structures for most of the residues in the three molecules are substantially the same. However, the courses of the three C-terminal tails are completely different, and the intermolecular interactions resulting from the particular packing of the molecules in the crystals account for the differences. The strand Be-2 and the preceding B-turn in small domain show large r.m.s. deviations among the three molecules and they are also involved in i The three-dimensional structure of trichosanthin at 2.7A resolution has been further further, by refitting one of the C-terminal tails, adjusting 16 residues in the molecular surface regions, discarding some water molecules with high B values, and adjusting weights during the further The R-factor has been reduced to 18.5% and the rms deviations from ideal geometry are also improved. The structures of the two molecules in the monoclinic asymmetric unit and the only molecule in the orthorhombic asymmetric unit are compared with one another. main-chain structures for most of the residues in the three molecules are substantially the same. However, the courses of the three C-terminal tails are completely different, and the intermolecular interactions resulting from the particular packing of the molecules in the crystals account for the differences. The strand Be-2 and the preceding B-turn in small domain show large rms deviations among the three molecules and they are also involved in i