CRYSTALLIZATION OF CYCLOMALTODEXTRIN GLUCANOTRANSFERASE FROM BACILLUS CIRCULANS VAR. ALKALOPHILUS. I. Kuranova, Institute of Crystallography, Moscow, Russia, P. Mattsson, T. Korpela, Biochemistry Department University of Turku, Turku, Finland

The crystallization of cyclomaltodextrin glucanotransferase from Bac. circulans var. alkalophilus (CGTase, EC 2.4.1.19) was studied in the presence of some low molecular weight compounds such as n-octyl beta-D-glucopyranoside (OG), 2-methyl-2,4-pentanediol (MPD), isopropanol, bivalent metal ions, alpha- and beta-cyclodextrin. Vapor diffusion technique was used for crystal growth. When ammonium sulfate (AS) and PEG 4000 were used as precipitants the protein was obtained in amorphous state only. When 3 % MPD was added into AS solution the microcrystalline tubes of CGTase were observed in electron microscope. The addition of 0.3 % of OG together with calcium chloride (0.5 mmol) to the PEG 4000 containing protein solution promoted the formation of thin needle-shaped crystals assembled into spherical druses. The substitution of calcium chloride for cobalt chloride in crystallization trials caused the formation of non-faceted spherical particles. When PEG 1500 or PEG 600 were used instead of PEG 4000 the bipyramidal crystals of size of 0.05 mm were obtained. The addition into protein solution of alpha- or beta-CD which are the products of enzymatic reaction reduced the amount of crystals in the drop and increased their size. The largest crystals up to 0.3 mm in each derection with limits of diffraction till 3 A were grown, when 10-15% of isopropanol was added into the reservoir solution.