PURIFICATION, CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION STUDIES OF C-PHYCOCYANIN AND ALLOPHYCOCYANIN FROM SPIRULINA-PLATENSIS

C-phycocyanin and allophycocyanin from the green alga Spirulina platen sis were isolated and crystallized by gel-acupuncture techniques. A no vel two-step chromatographic procedure was used for purification. Blue hexagonal crystals were obtained by diffusing magnesium chloride into the protein solution for a week, followed by diffusion of PEG 6000 in order to complete the reduction of the solubility of the protein in t he capillary tube used as a growth cell. In the case of allophycocyani n, crystals with a size of 0.4 x 0.3 x 0.3 mm were characterized by X- ray diffraction. They belong to space group P6(3)22 pith unit-cell par ameters a = b = 102.04, c = 131.22 Angstrom. The crystals of C-phycocy anin belong to either space group P6 or P6(3) with unit-cell constants a=b=182.38, c=60.87 Angstrom, alpha=beta=90, gamma=120 degrees. The c rystals diffract beyond 2.4 and 2.5 Angstrom resolution, respectively, using a rotating anode as an X-ray source.