CRYSTALLIZATION OF CHICKEN EGG-WHITE LYSOZYME FROM AMMONIUM-SULFATE

Chicken egg-white lysozyme was crystallized from ammonium sulfate over the pH range 4.0-7.8, with protein concentrations from 100 to 150 mg ml(-1). Crystals were obtained by vapor-diffusion or batch-crystalliza tion methods. The protein crystallized in two morphologies with an app arent morphology dependence on temperature and protein concentration. In general, tetragonal crystals could be grown by lowering the protein concentration or temperature. Increasing the temperature or protein c oncentration resulted in the growth of orthorhombic crystals. Represen tative crystals of each morphology were selected for X-ray analysis. T he tetragonal crystals belonged to the P4(3)2(1)2 space group with cry stals grown at pH 4.4 having unit-cell dimensions of a = b = 78.71, c = 38.6 Angstrom and diffracting to beyond 2.0 Angstrom. The orthorhomb ic crystals, grown at pH 4.8, were of space group P2(1)2(1)2 and had u nit-cell dimensions of a = 30.51, b = 56.51 and c = 73.62 Angstrom.