The crystal structure of tortoise egg-white lysozyme at 6 A resolution.

Lysozyme extracted from the egg-white of tortoise, the first example of a reptilian lysozyme to have been purified, has been crystallized and its tertiary structure determined at low resolution by X-ray analysis. This structure is shown to be closely homologous to that of hen egg-white lysozyme. The crystals of tortoise egg-white lysozyme contain a large proportion of liquid and the X-ray map shows that this forms large channels through the crystals into which the active sites of the enzyme molecules open. This indicates that tortois lysozyme crystals may be suitable for low-temperature studies of true enzyme substrate complexes.