Crystallization and preliminary X-ray study of a new crystal form of cytochrome c' from Rhodobacter capsulatus

A new crystal form of diheme cytochrome c' from Rhodobacter capsulatus has been obtained and preliminary crystallographic experiments have been performed. The crystals belong to the space group P2₁2₁2 with unit-cell dimensions of a = 47.82, b = 72.59, c = 34.32 Å. The assumption that an asymmetric unit of the crystal contains one half of the homodimer molecule indicates that the monomers in the dimeric molecule may be related by a crystallographic twofold axis. Crystals diffract up to 1.7 Å resolution using the X-ray beam from synchrotron radiation, and 11 127 unique structure factors were obtained with an R_merge of 7.1% from 52 922 indexed reflections. Structure analysis by means of molecular-replacement methods is now underway.