Crystallization of cytochrome b₅₆₂ from Erwinia chrysanthemi

Cytochrome b₅₆₂ from Erwinia chrysanthemi has been crystallized using the hanging-drop vapour-diffusion method with ammonium sulfate as the precipitant. X-ray precession photographs show that the crystals formed belong to either of the enantiomorphic space groups P4₁2₁2 or P4₃2₁2 with the cell parameters a = b = 98.6 and c = 62.7 Å. Estimation of the crystal density and consideration of the possible values for V_m indicate that there is either a dimer or trimer in the asymmetric unit. Experiments using the synchrotron radiation source at the CCLRC Daresbury Laboratory have shown that the crystals diffract to at least 2.7 Å resolution. An analysis of the N-terminal sequence indicates that this cytochrome shows limited homology to the cytochrome b₅₆₂ from E. coli. Determination of the structure will therefore allow analysis of the relationship between these two proteins.