Crystallization and preliminary crystallographic investigations of cytochrome c₄ from Pseudomonas stutzeri

Cytochrome c₄ from the bacterium Pseudomonas stutzeri has been crystallized and X-ray diffraction data have been collected to 2.2 Å resolution. The crystals belong to the monoclinic system, space group P2₁ with cell parameters a = 49.49, b = 58.58, c = 63.51 Å and β = 96.96°. The crystals contain two molecules it, the asymmetric unit. Cytochrome c₄ is known to contain two covalently bound haem groups per molecule and positions of the four haem Fe atoms in the asymmetric unit were determined from native anomalous-dispersion differences. The shortest Fe–Fe distances found in the crystal were 15.8, 16.9 and 19.0 Å.