Black beetle virus--crystallization and particle symmetry.

Black beetle virus, propagated in cultured Drosophila cells, crystallized into rhombic dodecahedra which diffracted X rays to 3.0 A resolution. Center-to-center spacing of particles in the unit cell was 305 A, while the spherically averaged diameter obtained from small-angle X-ray scattering from virus in solution was 312 A. Low resolution diffraction patterns from single crystals showed that the protein subunits are distributed centrosymmetrically, while electron microscopy indicated the particles are icosahedral in shape. The size of the particle is sufficient to accommodate about 180 protein subunits (44 kDa) consistent with T = 3 quasisymmetry.