Refined structure of trichosanthin at 1.73 A resolution

An X-ray reflection data set of the orthorhombic crystal of Trichosanthin (TCS) at 1.73 A resolution had been collected using the area detector. We determined TCS crystal structure by the molecular replacement method using the data of the known alpha-momocharin model and TCS intensities, and then TCS structure refinement at 1.73 A resolution was performed with the restrained least-squares refinement. A final R-factor of 0.186 was obtained with a model obeying standard geometry within 0.013 A in bond lengths and 2.48 degrees in bond angles. The final model contains 133 solvent molecules in the asymmetric unit. This paper gives a detailed description of TCS molecule structure, temperature factors, hydrogen bonds, bound water, the distribution of conserved residues and the interactions between the TCS molecules. The hydrogen bond between the hydroxyl group of conserved residue 14Tyr and O157 plays an important role in maintaining the active site conformation. Conserved residue 160Glu and its conformation at the active site play a key role in the catalytic activity.