REFINED STRUCTURE OF TRICHOSANTHIN AT 1.73 ANGSTROM RESOLUTION

An X-ray reflection data set of the orthorhombic crystal of Trichosant hin(TCS) at 1.73 Angstrom resolution had been collected using the area detector, We determined TCS crystal structure by the molecular replac ement method using the data of the known alpha-momorcharin model and T CS intensities, and then TCS structure refinement al 1.73 Angstrom, re solution was performed with the restrained least-squares refinement. A final R-factor of 0.186 was obtained with a model obeying standard ge ometry within 0.013 Angstrom, in bond lengths and 2.48 degrees in bond angles. The final model contains 133 solvent molecules in the asymmet ric unit. This paper gives a detailed description of TCS molecular str ucture, temperature factors, hydrogen bonds, bound water, the distribu tion of conserved residues and the interactions between the TCS molecu les. The hydrogen bond between the hydroxyl group of conserved residue 14Tyr and O-157 plays an important role in maintaining the active sit e conformation. Conserved residue 160Glu and its conformation at the a ctive site play a key role in the catalytic activity.