Expression, purification, crystallization and preliminary X-ray diffraction analysis of the effector-interaction domain of the resistance protein RGA5-A from Oryza sativa L. japonica.

RGA5-A, a component of the Pia resistance-protein complex (RGA4/RGA5-A) from Oryza sativa L. japonica, has the ability to interact physically with the effector protein AVR-Pia from Magnaporthe oryzae via its effector-interaction domain RGA5-A_S. The interaction between RGA5-A and AVR-Pia relieves the repression of RGA4, leading to AVR-independent cell death by the freed RGA4. To further understand the details of this interaction, the effector-interaction domain RGA5-A_S was expressed in Escherichia coli and purified to homogeneity. The purified recombinant protein His-RGA5-A_S was successfully crystallized using the sitting-drop vapour-diffusion method. A single crystal obtained using 0.2 M ammonium citrate, 25%(w/v) PEG 3350 diffracted to 2.43 Å resolution. It belonged to space group P4122 or P4322, with unit-cell parameters a = b = 55.2, c = 78.2 Å, α = β = γ = 90°.