The pita gene (PA4866) was amplified by PCR from Pseudomonas aeruginosa PAC1 (8602) genomic DNA and cloned into the NdeI and BamHI sites of vector pET 24a (Novagen). PAC1 displays minor sequence differences compared with strain PAO1 in the Pseudomonas genome database. In gene PA4866, the only difference between the two strains is the nucleotide change (PAO1) A139G (PAC1), resulting in the amino acid change T47A. Recombinant plasmid DNA was used to transform met-Escherichia coli strain B834 (DE3) (Novagen). Cells were grown in 400 mL methionine-supplemented M9 medium to an OD600 = 1, resuspended in fresh medium without methionine, and grown at 37°C for 6 h before adding 50 mg Se-met followed, after 30 min, by 1 mM IPTG. After 9.5 h growth at 37°C, cells were harvested by centrifugation, resuspended in 20 mL cold 50 mM Tris buffer, pH 7.2, 1 mM EDTA, 1 mM DTT, pH 7.2 (TED). After sonication, addition of 0.2 g streptomycin sulphate and centrifugation, 45% (w/v) ammonium sulphate was added to the supernatant. The precipitate was dissolved and dialysed against cold TED before loading on a Q-Sepharose (2 × 15 cm) column. Protein was eluted with a 400 mL linear gradient of 0–0.3 M NaCl in TED buffer, and the peak of 280 nm absorbing material eluting at 0.15 M NaCl was bulked and precipitated with 70% (w/v) ammonium sulphate. The precipitate was dissolved in TED (2 mL), loaded on a Sephacryl 200 column (26 × 600 mm), and eluted with TED containing 0.15 M NaCl. Peak fractions (280 nm) were bulked, and the protein precipitated with ammonium sulphate (70% (w/v)) then dissolved in 0.25 mL TED and dialyzed against TED.