Figure 3

Immunoblot analysis of Obg of M. tuberculosis. A. Immunoblot analysis of Obg from M. tuberculosis strains harboring plasmids. M. tuberculosis strains were grown in 7H9-OADC-TW broth at 37°C to early log phase and lysates prepared using a bead beater and separated (100 μg protein for each lane) on SDS-PAGE. The immunoblots were probed with anti-Obg antiserum (1:500 dilution) followed by alkaline phosphatase labeled anti-rabbit IgG (1:1000 dilution, Zymed). The antibody-incubated blots were then developed with NBT/BCIP substrates. Lane 1, M. tuberculosis carrying the plasmid pMV261(empty vector control); Lane 2, M. tuberculosis carrying the plasmid pMVOBG (plasmid overexpressing Obg). B. Immunoblot analysis of Obg at different growth points in M. tuberculosis culture. Wild type M. tuberculosis was grown in 7H9-OADC-TW broth at 37°C. Lysates were prepared from wild-type M. tuberculosis grown to different ODs at 600 nm, separated (200 μg protein for each lane) on SDS-PAGE, and probed with anti-Obg antiserum (1:500 dilution) followed by peroxidase-labeled anti-rabbit IgG (1:10,000 dilution, Sigma). The blots were developed with an ECL kit (Amersham) and autoradiographed. "Obg" indicates the Obg protein reacting with anti-Obg antiserum. Values below each band indicate the OD value at 600 nm at the time of harvest. The graph above the bands gives the levels of Obg, based on density of the bands using Image J software. C. Immunoblots of Obg in separated soluble vs membrane fractions of M. tuberculosis lysates. The bacteria were grown in 7H9-OADC-TW broth at 37°C to mid-log phase. Lysates were prepared using a bead beater, and the soluble and pellet fractions separated by centrifugation. The protein fractions (200 μg protein for each lane) were separated by SDS-PAGE, blotted and probed with anti-Obg antiserum (1:500 dilution) (marked as Obg) or anti-SigH antiserum (1:1000 dilution) (marked as SigH), followed by peroxidase-labeled anti-rabbit IgG (1:10,000 dilution, Sigma). The blots were developed with an ECL kit (Amersham) and autoradiographed. In the figure, lanes labeled Whole, Supernatant and Pellet represent extracts of whole M. tuberculosis, of the 49,000 g supernatant, and of the 49,000 g pellet, respectively.