Crystallization and X-ray diffraction analysis of the C-terminal domain of the flax rust effector protein AvrM

The flax rust effector AvrM is a secreted protein of unknown fold that is recognized by the M resistance protein in flax. In order to investigate the structural basis of the AvrM-M interaction and possible virulence-associated functions of AvrM, the C-terminal domains of two different AvrM variants (AvrM-A and avrM) were crystallized. Crystals of native AvrM-A were obtained using pentaerythritol ethoxylate (15/4 EO/OH) as a precipitant and diffracted X-rays to 2.9 Å resolution. Selenomethionine-derivative crystals of similar quality were obtained using PEG 1500 as a precipitant. Both the native and selenomethionine-labelled AvrM-A crystals had symmetry of space group C222₁ with eight molecules in the asymmetric unit. Crystals of avrM had symmetry of space group P2₁2₁2₁ and diffracted X-rays to 2.7 Å resolution. Initial AvrM-A phases were calculated using the single-wavelength anomalous dispersion (SAD) method and a partial model was built. Phases for avrM were obtained by molecular replacement using the partial AvrM-A model.