Study on the crystallization conditions of lysozyme from three different species

Obtaining diffraction quality protein crystals is the bottleneck of protein structure analysis. In order to improve crystallization efficiency, crystallization conditions of hen-egg white, Bacillus and human lysozymes were studied. The solubilities of lysozymes from the three species at different pH values and temperatures were analyzed. The effects of initial lysozyme concentration, temperatures, pH values and precipitants on crystallization were then investigated by the sitting drop vapor diffusion method. The results indicate that the profiles of lysozyme solubility, the optimal crystallization conditions and the crystal forms from three different species are all different. The optimal crystallization conditions for lysozyme from hen-egg white and Bacillus are as follows: the initial concentration of lysozyme = 40 mg∙mL-1, 25 ℃, pH value = 5.5 and precipitants = 0.1 mol∙L-1 sodium acetate and 2.0 mol∙L-1 sodium formate. For human lysozyme: 80 mg∙mL-1, 25 ℃, pH value = 6.1 and precipitants = 0.1 mol∙L-1 BIS-TRIS and 2 mol∙L-1 ammonium sulfate. The crystal forms of hen-egg white, Bacillus and human lysozymes are square, plate and needle, respectively. The results demonstrate that the optimization of the crystallization conditions can improve protein crystallization efficiency and is helpful to study structure, function and mechanism of proteins. © 2020, Editorial Board of "Journal of Chemical Engineering of Chinese Universities". All right reserved.