Samples were taken at different intervals for absorbance readings at 600 nm and β-galactosidase activity determinations. The growth medium for strains carrying pTZlipA or pTZ110 was amended with carbenicillin and for the lipR and rpoN mutant strains also with tetracycline. Cells were permeabilized with CHCl3 and sodium dodecyl sulfate. Production of LipR from pME6032LipR in Ps93 was induced with 0.5 mM IPTG at A600 nm 0.5, and the incubation continued for 15 h at 20 °C. Harvested cells were resuspended and lysed by sonication in 50 mM sodium phosphate, pH 6.0, 2 mM EDTA, 0.5 mg mL−1 lysozyme, 10% glycerol, and complete mini

protease inhibitor (Roche). Cell debris was removed by centrifugation (60 min at 17 000 g, 4 °C). The cell-free extract was subjected

to affinity chromatography using heparin sepharose (GE Healthcare) GSI-IX in vitro and eluted with a 0-1 M NaCl gradient in 50 mM sodium phosphate, pH 6.0, 10% glycerol, and 10 mM beta-mercaptoethanol. selleck Pooled fractions, after addition of 1 M ammonium sulfate, were loaded on a phenyl–Sepharose column (GE Healthcare) and eluted with a 1-0 M ammonium sulfate gradient in 50 mM sodium phosphate, pH 8.0, 10% glycerol, 10 mM beta-mercaptoethanol. Pooled fractions were concentrated (Vivaspin) and subjected to gel filtration (Superdex 75 HR 16/60 column) in 50 mM Tris–HCl, pH 8.0, 20 mM NaCl, 10% glycerol, and 10 mM beta-mercaptoethanol. Purified LipR was up to > 95% pure, as judged by Coomassie stained SDS-PAGE analysis. LipR was phosphorylated by use of a low-molecular-weight phosphate donor, carbamoyl phosphate. The reaction was performed at 37 °C for 1 h in a buffer consisting of 50 mM Tris–HCl, pH 7.0,

7.5 mM MgCl2, 1 mM DTT, and 50 mM disodium carbamoyl phosphate. Directly after this phosphorylation reaction, the LipR-P protein was used in a SPR experiment, MS analysis, or ATPase assay. A standard ATPase assay was performed at 37 °C in a final reaction volume of 50 μL of 50 mM Tris–HCl, pH 7.0, and 5 mM MgCl2. Reactions were initiated by addition of ATP mixed with [γ-32P]ATP (Amersham) to a final concentration of 20 nM ATP (~100 000 cpm pmol−1). Incubations were performed for 40 min with various concentrations Immune system of purified LipR and DNA fragment PlipA199. The reactions were terminated by addition of 50 μL 5% (w/v) of activated charcoal in 1 M HCl, which adsorbs proteins and nucleotides, but not inorganic phosphate (Parlato et al., 1981). The samples were centrifuged (2 min, 11 000 g, 4 °C), thereafter 50 μL of the supernatant was quickly but carefully transferred to another tube, which was centrifuged once more after which 25 μL of the supernatant was used for quantification of released 32Pi by liquid scintillation counting (Packard). Immediately after in vitro phosphorylation, LipR-P was precipitated with chloroform/methanol and stored at −80 °C. The protein pellet was dissolved in 6 M urea, 50 mM bicarbonate buffer, pH 7.