Crystallization and preliminary X-ray diffraction studies of cytochrome c6 from Porphyra yezoensis

Cytochrome c(6) from the red alga Porphyra yezoensis has been purified and crystallized by the sitting-drop vapour-diffusion method. Two different crystal forms, tetragonal and orthorhombic, were obtained. The tetragonal crystals belong to space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell dimensions a = 49.33 (2), c = 83.70 (10) A. The orthorhombic crystals belong to space group P2(1)2(1)2(1), with unit-cell dimensions a = 46.74 (2), b = 49.42 (1), c = 37.11 (1) A. Absorption spectra of the crystals showed that the tetragonal form was oxidized and the orthorhombic form was reduced.