Methods Bacterial strains The two mycobacterial reference SBI-0206965 price strains, M. tuberculosis H37Ra (MNC 16394) and M. tuberculosis H37Rv (ATCC 27294), used in this study were kindly provided by Dr Harleen Grewal, The Gade Institute, University of Bergen, Norway. The strains had undergone less than 3 passages in the laboratory before being used for this study. The bacilli were cultured on Middelbrook 7H10 agar plates with OADC enrichment (BD Difco) at 37°C and 5% CO2 for 3-4 weeks. Bacterial colonies were harvested by using an extraction buffer consisting of
phosphate-buffered saline (PBS), pH 7.4 with freshly added Roche Protease Inhibitor Cocktail (1 μg/ml) (Complete, EDTA-free, Roche Gmbh, Germany). Six hundred μl of this extraction buffer was added to each agar plate and the mycobacterial colonies were gently scraped off the agar surface using a cell scraper. Aliquots of the resulting pasty bacterial mass were transferred into 2 ml cryotubes with O-rings (Sarstedt, Norway) containing 250 μl of acid washed glass beads (≤106 μm; Sigma-Aldrich, Norway) and an additional 600 μl of extraction buffer containing a cocktail of protease inhibitors (1 μg/ml) (Roche Diagnostics GmbH), and stored at -80°C until further treatment. For protein extraction, the mycobacteria were disrupted mechanically by bead-beating in a Ribolyser (Hybaid, UK) at max speed (6.5) for
45 seconds. Triton X-114 extraction of exported proteins from whole bacteria Triton X-114 phase-partitioning was used to isolate lipophilic proteins following the method of Bordier
[20] Ferrostatin-1 nmr and a modified version for extraction of lipophilic proteins from whole bacilli [21]. Briefly, 3-4 week old bacilli were lysed by bead-beating and unbroken cells and cell-wall debris were removed by centrifugation at 2300 g for 5 minutes. Triton X-114 was added to the supernatant (final detergent concentration 2%, w/v) and the suspension was stirred at 4°C for 30 minutes. PARP inhibitor Residual insoluble materials over were removed by centrifugation at 15700 g for 10 min at 4°C. For separation of the hydrophobic and hydrophilic proteins, the solution was incubated at 37°C for 15 minutes, the solution separated into two phases, an upper aqueous phase containing hydrophilic proteins, and a lower (detergent) phase containing the hydrophobic proteins. Proteins in the lower detergent phase were precipitated by acetone. Gel electrophoresis and in-gel digestion of proteins Extracted proteins, 50 μg from each strain, were mixed with 25 μl sodium-dodecyl-sulphate (SDS) loading buffer and boiled for 5 minutes before separation on a 10 cm long 1 mm thick 12% SDS polyacrylamide gel. The protein migration was allowed to proceed until the bromophenol dye had migrated to the bottom of the gel. The protein bands were visualized with Coomassie Brilliant Blue R-250 staining (Invitrogen, Carlsbad, CA, U.S.A.).