Crystallization and preliminary X-ray diffraction analysis of the arginine repressor of the hyperthermophile Thermotoga neapolitana.

The arginine repressor of Thermotoga neapolitana (ArgRTnp) is a member of the family of multifunctional bacterial arginine repressors involved in the regulation of arginine metabolism. This hyperthermophilic repressor shows unique DNA-binding features that distinguish it from its homologues. ArgRTnp exists as a homotrimeric protein that assembles into hexamers at higher protein concentrations and/or in the presence of arginine. ArgRTnp was crystallized with and without its corepressor arginine using the hanging-drop vapour-diffusion method. Crystals of the aporepressor diffracted to a resolution of 2.1 A and belong to the orthorhombic P2(1)2(1)2(1) space group, with unit-cell parameters a = 117.73, b = 134.15, c = 139.31 A. Crystals of the repressor in the presence of its corepressor arginine diffracted to a resolution of 2.4 A and belong to the same space group, with similar unit-cell parameters.