Abstract
In plants, the nucleocytoplasmic protein EDS1 (Enhanced disease susceptibility1) is an important regulator of innate immunity, coordinating host-cell defence and cell-death programs in response to pathogen attack. Arabidopsis thaliana EDS1 stabilizes and signals together with its partners PAD4 (Phytoalexin deficient4) and SAG101 (Senescence-associated gene101). Characterization of EDS1 molecular configurations in vitro and in vivo points to the formation of structurally and spatially distinct EDS1 homomeric dimers and EDS1 heteromeric complexes with either PAD4 or SAG101 as necessary components of the immune response. EDS1, PAD4 and SAG101 constitute a plant-specific protein family with a unique `EP' (EDS1-PAD4-specific) domain at their C-termini and an N-terminal domain resembling enzymes with an α/β-hydrolase fold. Here, the expression, purification and crystallization of a functional EDS1 complex formed by EDS1 and SAG101 from Arabidopsis thaliana are reported. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 101.8, b = 115.9, c = 122.8 Å, and diffracted to 3.5 Å resolution.