DETERMINATION AND REFINEMENT OF THE CANINE PARVOVIRUS EMPTY-CAPSID STRUCTURE

The canine parvovirus (CPV) empty-capsid structure has been determined and refined to 3.0 Angstrom resolution in the tetragonal space group P4(3)2(1)2 with cell dimensions a = b = 254.5 and c = 795.0 Angstrom. The successful structure determination shows that reasonably good diff raction data were obtained in spite of the very long c axis. The struc ture was solved by molecular replacement using the electron density of CPV full particles in a monoclinic space group. The phases were refin ed by non-crystallographic symmetry averaging. The structure refinemen t was carried out by using the programs PROLSQ and X-PLOR. The final R factor for the structure that included 85 water molecules per icosahe dral asymmetric unit was 21.1% for reflections between 6.0 and 3.0 Ang strom resolution with an r.m.s. deviation of bond lengths of 0.020 Ang strom from ideal values. The structure of CPV empty capsids showed con formational differences with respect to full capsids at a region where icosahedrally ordered DNA in full particles interacts with the capsid protein. It also confirmed the absence of density along the fivefold axis in the CPV empty-particle structure in contrast to the situation in CPV full particles.