Crystallography of succinimide hen egg-white lysozyme at low temperatures

In order to elucidate the mechanism of the succinimide formation at Asp 101 in hen egg-white lysozyme, 101-succinimide lysozyme was purified and crystallized using NaCl as a precipitant. The 101-succinimide protein was considerably less soluble in NaCl solutions than the native protein. The crystals belong to the tetragonal space group P4(3)2(1)2 with cell parameters of a = 78.96 Angstrom and c = 38.09 Angstrom and are isomorphous with those of the native protein. The formation of the less soluble 101-succinimide protein in NaCl solutions and in crystalline states is pointed out to be taken into account in crystallization studies of lysozyme. Although the regeneration of the native protein from the 101-succinimide protein took place even in the crystalline states at room temperature, it was virtually suppressed at 4 degrees C. X-ray diffraction data for the crystal of the 101-succinimide protein have been collected at 4 degrees C. The three-dimensional structure analysis of the crystal is in progress.