Purification, crystallization and preliminary crystallographic studies of an integral membrane protein, cytochrome bo(3) ubiquinol oxidase from Escherichia coli

Cytochrome bo(3) ubiquinol oxidase has been successfully purified for cryst allization. Single crystals of this integral membrane protein diffract X-ra ys to 3.5 Angstrom resolution and belong to the orthorhombic space group C2 22(1). From the diffraction data, the unit-cell parameters were determined to be a = 91.3, b = 370.3, c = 232.4 Angstrom. The crystals have a solvent content of 59% and contain two molecules per asymmetric unit. A search mode l generated from the structures of cytochrome c oxidase from Paracoccus den itrificans and the extrinsic domain of cytochrome bo(3) ubiquinol oxidase f rom Escherichia coli was used for molecular-replacement studies, resulting in a solution with sensible molecular packing.