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

A plastocyanin from the cyanobacterium Synechococcus sp. PCC7942 has been crystallized in two different forms by hanging-drop vapour diffusion with ammonium sulfate as precipitant. Form I is hexagonal, space group P6₁ or P6₅, with unit-cell dimensions a = b = 34.62 and c = 107.22 Å. Form II is tetragonal, space group P4₁ or P4₃, with unit-cell dimensions a = b = 43.05 and c = 56.94 Å. Form I crystals diffract to 2.5 Å using graphite-monochromated Cu Kα radiation from a Rigaku RU-300 rotating-anode generator operated at 40 kV and 100 mA. Form II crystals diffract to 1.9 Å using synchrotron radiation at beamline BL6A of the Photon Factory (KEK). Molecular-replacement calculations using the structure of plastocyanin from Ulva pertusa have been performed.