Expression, purification, crystallization and preliminary X-ray analysis of the extracellular sensory domain of DraK histidine kinase from Streptomyces coelicolor

The bacterium Streptomyces coelicolor produces useful antibiotics from its secondary metabolites. DraK is a sensory histidine kinase involved in the differential regulation of antibiotics in S. coelicolor through the DraR/DraK two-component system. Here, the extracellular sensory domain of DraK was overexpressed in Escherichia coli, purified and crystallized using the sitting-drop vapour-diffusion method. The crystal diffracted to 2.2 angstrom resolution and belonged to space group C222(1), with unit-cell parameters a = 41.91, b = 174.50, c = 145.25 angstrom, alpha = beta = gamma = 90 degrees.