Crystallization and preliminary X-ray analysis of the chemokine-binding protein from orf virus (Poxviridae).

The parapoxvirus orf virus (ORFV) encodes a chemokine-binding protein (CBP) that functions to downregulate the host's immune response at the site of infection by blocking the chemokine-induced recruitment of immune cells. In order to shed light on the structural determinants of CBP-chemokine binding, ORFV CBP was crystallized as part of an ongoing structure-function study on this protein. ORFV CBP crystals were obtained by the sitting-drop vapour-diffusion technique using ammonium citrate as a precipitant. The crystal quality was greatly improved through the addition of small-molecule additives to the crystallization mother liquor. ORFV CBP crystals diffracted X-rays to 2.50 A resolution and belonged to the hexagonal space group P6(1)22 or its enantiomorph P6(5)22, with unit-cell parameters a = b = 75.62, c = 282.49 A, alpha = 90, beta = 90, gamma = 120 degrees.