Crystallization and preliminary X-ray analysis of plastocyanin from cyanobacterium Synechococcus sp. PCC 7942

A plastocyanin from the cyanobacterium Synechococcus sp. PCC7942 has been c rystallized in two different forms by hanging-drop vapour diffusion with am monium sulfate as precipitant. Form I is hexagonal, space group P6(1) or P6 (5), with unit-cell dimensions a = b = 34.62 and c = 107.22 Angstrom. Form II is tetragonal, space group P4(1) or P4(3), with unit-cell dimensions a = b = 43.05 and c = 56.94 Angstrom. Form I crystals diffract to 2.5 Angstrom using graphite-monochromated Cu K alpha radiation from a Rigaku RU-300 rot ating-anode generator operated at 40 kV and 100 mA. Form II crystals diffra ct to 1.9 Angstrom using synchrotron radiation at beamline BL6A of the Phot on Factory (KEK). Molecular-replacement calculations using the structure of plastocyanin from Ulva pertusa have been performed.