USE OF CHEMICAL MODIFICATION IN THE CRYSTALLIZATION OF ISOCITRATE LYASE FROM ESCHERICHIA-COLI

Two different crystal forms of isocitrate lyase (ICL) from Escherichia coli have been grown following the chemical modification of the enzyme by either 3-bromopyruvate or ethyl mercuri thiosalicylate (EMTS) contrasting strongly with difficulties in obtaining ordered crystals of the native enzyme. Both crystal forms are obtained using the hanging drop method of vapour diffusion with ammonium sulphate as the precipitant. The crystals diffract well and X-ray photographs of the crystals have established that they are in space groups C2221 and P31 (or its enantiomorph P32) respectively. Considerations of the values of Vm and measurements on the crystal density indicate that the asymmetric unit of both crystals contains four subunits. © 1991.