Preliminary X-ray Study of Crystals Obtained by Co-Crystallization of Hypoxanthine‒Guanine Phosphoribosyltransferase from Escherichia coli and Pyrazine-2-Carboxamide Derivatives

A highly effective producer strain Escherichia coli C3030/pET23d + - Ec HGPRT, allowing production of recombinant hypoxanthine‒guanine phosphoribosyltransferase from E. coli ( Ec HGPRT) in a soluble form, has been created. A method for isolating and purifying the recombinant protein has been developed. The specific activity against the natural substrate and pyrazine-2-carboxamide derivatives has been determined. Crystals of the Ec HGPRT complexes with 3-hydroxypyrazine-2-carboxamide (T-1105) and 6-fluoro-3-hydroxypyrazine-2-carboxamide (T-705), suitable for X-ray diffraction analysis, have been grown by capillary counter diffusion. X-ray diffraction sets with a resolution of up to 2.4 and 2.5 Å have been collected at the ESRF synchrotron (France, station ID23-1) at a temperature of 100 K. The crystals belong to the sp. gr. P 3(1)21; the independent part of the cell contains two enzyme molecules.