Cloning, expression, refolding, purification and preliminary crystallographic analysis of the sensory domain of the Campylobacter chemoreceptor for aspartate A (CcaA)

In Campylobacter jejuni, chemotaxis and motility have been identified as important virulence factors that are required for host colonization and invasion. Chemotactic recognition of extracellular signals is mediated by the periplasmic sensory domains of its transducer-like proteins (Tlps). In this study, the sensory domain of the C. jejuni chemoreceptor for aspartate A (CcaA) has been expressed in Escherichia coli and purified from inclusion bodies. The urea-denatured protein was refolded and then crystallized by the hanging-drop vapour-diffusion method using PEG 3350 as a precipitating agent. A complete data set has been collected to 1.4 Å resolution using cryocooling conditions and synchrotron radiation. The crystals belonged to space group P1, with unit-cell parameters a = 39.3, b = 43.3, c = 50.9 Å, α = 92.5, β = 111.4, γ = 114.7°.