Crystallization and preliminary X-ray diffraction analysis of the arginine repressor ArgR fromBacillus halodurans

Abstract

The arginine repressor (ArgR) is a transcriptional regulator which regulates genes encoding proteins involved in arginine biosynthesis and the arginine catabolic pathway. ArgR from the alkaliphilic bacteriumBacillus haloduranswas cloned and overexpressed inEscherichia coli. ArgR (Bh2777) fromB. haloduransis composed of 149 amino-acid residues with a molecular mass of 16 836 Da. ArgR was crystallized at 296 K using 1,2-propanediol as a precipitant. Crystals of N-terminally His-tagged ArgR were obtained by the sitting-drop vapour-diffusion method. Dehydrated crystals showed a dramatic improvement in diffraction quality and diffracted to 2.35 Å resolution. The crystals belonged to the cubic space groupI23, with unit-cell parametersa=b=c= 104.68 Å. The asymmetric unit contained one monomer of ArgR, which generates a trimer by the threefold axis of the space group, giving a crystal volume per mass (VM) of 2.98 Å3 Da−1and a solvent content of 56.8%.