Production, biophysical characterization and crystallization of Pseudomonas putida GraA and its complexes with GraT and the graTA operator

The graTA operon from Pseudomonas putida encodes a toxin–antitoxin module with an unusually moderate toxin. Here, the production, SAXS analysis and crystallization of the antitoxin GraA, the GraTA complex and the complex of GraA with a 33 bp operator fragment are reported. GraA forms a homodimer in solution and crystallizes in space group P2₁, with unit-cell parameters a = 66.9, b = 48.9, c = 62.7 Å, β = 92.6°. The crystals are likely to contain two GraA dimers in the asymmetric unit and diffract to 1.9 Å resolution. The GraTA complex forms a heterotetramer in solution. Crystals of the GraTA complex diffracted to 2.2 Å resolution and are most likely to contain a single heterotetrameric GraTA complex in the asymmetric unit. They belong to space group P4₁ or P4₃, with unit-cell parameters a = b = 56.0, c = 128.2 Å. The GraA–operator complex consists of a 33 bp operator region that binds two GraA dimers. It crystallizes in space group P3₁ or P3₂, with unit-cell parameters a = b = 105.6, c = 149.9 Å. These crystals diffract to 3.8 Å resolution.