Expression, purification, crystallization and preliminary X-ray diffraction analysis of a ribokinase from the thermohalophileHalothermothrix orenii
A ribokinase gene (rbk) from the anaerobic halothermophilic bacteriumHalothermothrix oreniiwas cloned and overexpressed inEscherichia coli. The recombinant protein (Ho-Rbk) was purified using immobilized metal-ion affinity chromatography and crystals were obtained using the sitting-drop method. Diffraction data were collected to a resolution of 3.1 Å using synchrotron radiation. The crystals belonged to the orthorhombic space groupP212121, with unit-cell parametersa= 45.6,b= 61.1,c= 220.2, and contained two molecules per asymmetric unit. A molecular-replacement solution has been found and attempts are currently under way to build a model of the ribokinase. Efforts to improve crystal quality so that higher resolution data can be obtained are also being considered.