Cloning, expression, purification, crystallization and preliminary X-ray crystallo­graphic study of GK0767, the copper-containing nitrite reductase from Geobacillus kaustophilus

The soluble region (residues 32-354) of GK0767, a copper-containing nitrite reductase from the thermophilic Gram-positive bacterium Geobacillus kaustophilus HTA426, has been cloned and overexpressed in Escherichia coli. The purified recombinant protein was crystallized using the hanging-drop vapour-diffusion method. X-ray diffraction data were collected and processed to a maximum resolution of 1.3 Å. The crystals belonged to space group R3, with unit-cell parameters a = b = 115.1, c = 87.5 Å. Preliminary studies and molecular-replacement calculations reveal the presence of one subunit of the homotrimeric structure in the asymmetric unit; this corresponds to a V_M value of 3.14 Å³ Da^-1.