Purification, characterization and preliminary crystallographic studies of a novel plant defensin from Pachyrrhizus erosus seeds

Defensins are small cysteine-rich antimicrobial peptides that are widely distributed in plants, insects and mammals. As potent defenders in protecting plants from pathogenic fungal attack, plant defensins are presumed to play an important role in the innate immunity of plants and are expected to find applications in the production of transgenic crops. A novel plant defensin protein SPE10 from Pachyrrhizus erosus seeds was purified and partially sequenced. Crystallization screening using the hanging-drop vapour-diffusion method resulted in two crystal forms, from one of which a diffraction data set was collected to 0.98 Å resolution. The crystal belongs to space group P2₁, with unit-cell parameters a = 32.71, b = 28.11, c = 54.85 Å, β = 103.78°. Preliminary crystallographic studies revealed two subunits in the asymmetric unit.