Purification, crystallization and preliminary X-ray crystallographic analysis of the phosphatase domain (PA3346PD) of the response regulator PA3346 from Pseudomonas aeruginosa PAO1

The phosphatase domain (PA3346PD) of the response regulator PA3346 modulates the downstream anti-anti-σ factor PA3347 to regulate swarming motility in Pseudomonas aeruginosa PAO1. PA3346PD, which comprises the protein phosphatase 2C domain (PP2C), is classified as a Ser/Thr phosphatase of the Mg²⁺- or Mn²⁺-dependent protein phosphatase (PPM) family. The recombinant PA3346PD, with molecular mass 26 kDa, was overexpressed in Escherichia coli, purified on an Ni²⁺–NTA agarose column and crystallized by the sitting-drop vapour-diffusion method. X-ray diffraction data were collected from PA3346PD crystals to a resolution of 2.58 Å and the crystals belonged to space group I4₁32 or I4₃32, with unit-cell parameter a = 157.61 Å. Preliminary analysis indicates the presence of a monomer of PA3346PD in the asymmetric unit with a solvent content of 58.4%.