CRYSTALLIZATION OF MITOCHONDRIAL CYTOCHROME B-C(1) COMPLEX FROM GEL WITH OR WITHOUT REDUCED PRESSURE

Cytochrome b-c(1) complex (ubiquinol-cytochrome c reductase) of beef heart mitochondria has been crystallized. Crystals grown in capillary tubes diffracted X-rays from a laboratory source to a resolution of 7 Angstrom and synchrotron radiation to a resolution of 4.5 Angstrom in the presence of mother liquor. However the movement of crystals in the mother liquor makes data collection very difficult. Removal of the mother liquor from the crystals causes severe loss of diffraction quality. To circumvent these difficulties we have recently developed a method for crystallization of the cytochrome b-c(1) complex from a gel. The sizes, shapes and diffraction qualities of crystals grown in gel approach those of crystals obtained from liquid. Preliminary experiments on a Xuong-Hamlin area detector indicate that these crystals have the symmetry of a body centered tetragonal space group with cell constants a = b = 157 Angstrom, c = 590 Angstrom. Assuming eight cytochrome b-c(1) complex dimers per unit cell, the crystals have a solvent content of 70% (v/v). Under reduced pressure the crystallization time is significantly decreased. Although crystals obtained under reduced pressure are generally smaller, the shorter crystallization time provides an opportunity to explore more crystallization conditions.