ATOMIC-STRUCTURE AT 2.5 ANGSTROM RESOLUTION OF URIDINE PHOSPHORYLASE FROM ESCHERICHIA-COLI AS REFINED IN THE MONOCLINIC CRYSTAL-LATTICE

Uridine phosphorylase from E, coli (Upase) has been crystallized using vapor diffusion technique in a new monoclinic crystal form, The struc ture was determined by the molecular replacement method at 2.5 Angstro m resolution, The coordinates of the trigonal crystal form were used a s a starting model and the refinement by the program XPLOR led to the R-factor of 18.6%, The amino acid fold of the protein was found to be the same as that in the trigonal crystals, The positions of flexible r egions were refined, The conclusion about the involvement in the activ e site is in good agreement with the results of the biochemical experi ments.