Parameters for the two-dimensional crystallization of the membrane protein microsomal glutathione transferase

Various crystallization parameters were investigated to obtain two-dimensional crystals of the detoxification enzyme microsomal glutathione transferase for structural analysis by electron crystallography. The protein was crystallized by reconstitution of the solubilized trimer into proteoliposomes. Crystallization occurs when minimal amounts of lipid in the range of three lipid molecules per protein trimer are added to the dialysate. Once crystals were obtained, the effect of several parameters on the crystallization was determined. The temperature and initial detergent concentration were found to be crucial parameters in influencing the size of the crystals, and conclusions could be drawn about the rate dependence of the crystallization process. Two highly ordered crystal forms, which are suitable for structural analysis by electron crystallography, were obtained under the two-dimensional crystallization conditions described here.