Expression, purification and crystallization of a novel nonstructural protein VP9 from white spot syndrome virus

The nonstructural protein VP9 from white spot syndrome virus (WSSV) has been identified and expressed in Escherichia coli. Native protein was purified and crystallized by vapour diffusion. The nonstructural protein VP9 from white spot syndrome virus (WSSV) has been identified and expressed in Escherichia coli. To facilitate purification, a cleavable His₆ tag was introduced at the N-terminus. The native protein was purified and crystallized by vapour diffusion against mother liquor containing 2 M sodium acetate, 100 mM MES pH 6.3, 25 mM cadmium sulfate and 3% glycerol. Crystals were obtained within 7 d and diffracted to 2.2 Å; they belonged to space group P2₁2₁2₁, with unit-cell parameters a = 74.13, b = 78.21, c = 78.98 Å and four molecules in the asymmetric unit. The selenomethionine-labelled protein produced isomorphous crystals that diffracted to approximately 3.3 Å