coli. Rv1096 was also ligated to the NdeI and HindIII sites of pVV2 (Colorado State University, USA) to obtain the pVV2-Rv1096 M. smegmatis expression
plasmid (Table 1). Table 1 Bacteria and plasmids Bacteria and plasmids Relevant characteristic(s) Resource Strains E. coli NovaBlue Used for cloning and propagation of plasmids Novagen E. coli ER2566 Used for expression of Rv1096 find more protein Novagen M. smegmatis mc2155 strain, used for expression of Rv1096 protein and preparation of peptidoglycan ATCC E. coli ER2566/Rv1096 E. coli ER2566 carrying pColdII-Rv1096 plasmid This work M. smegmatis/Rv1096 M. smegmatis mc2155 carrying pVV2-Rv1096 plasmid This work Plasmids pJET1.2/blunt vector Carries amp R gene; used for cloning PCR product Fermentas pColdII-Rv1096 Carries amp R gene; used for expression Rv1096 protein in E. coli ER2566 This work pVV2-Rv1096 selleckchem Carries kan R gene; used for expression of Rv1096 protein in M. smegmatis mc2155 This work Expression and purification of Rv1096 protein The pColdII-Rv1096 plasmid was transformed into E. coli ER2566 cells (Novagen) by a chemical transformation method . E.
coli ER2566 harboring the pColdII-Rv1096 plasmid (ER2566/Rv1096, Table 1) was grown in 300 ml of LB broth containing ampicillin (100 μg/ml) at 37°C. Isopropyl-D-thiogalactopyranoside at a final concentration of 1 mM was added to the culture when the OD600 reached 0.5, after which the culture was incubated at 16°C for 24 h. The pVV2-Rv1096 plasmid was transformed into M. smegmatis mc2155 using
an electroporation method . M. smegmatis mc2155 harboring the pVV2-Rv1096 plasmid (M. smegmatis/Rv1096, Table 1) was grown in 300 ml of LBT broth with kanamycin at 50 μg/ml at 37°C for 24 h. The cultures were centrifuged at 5000 × g for 15 min and the cell pellets were resuspended in 5 ml of lysis buffer (500 mM Tris-HCl, pH 8.0, 20 mM NaCl and 20% glycerol) with 1 mM phenylmethyl sulfonyl fluoride. After sonication, the lysates were centrifuged Dimethyl sulfoxide at 15000 × g for 20 min and the supernatant fraction was loaded onto a Ni-NTA column (Qiagen, Hilden, Germany) by gravity flow. The column was washed with 20 ml of wash buffer (20 mM Tris-HCl, pH 8.0, 500 mM NaCl, 20% glycerol and 30 mM imidazole). The purified protein was eluted with 10 ml of elution buffer (20 mM Tris-HCl, pH 8.0, 500 mM NaCl and 200 mM imidazole), and the first 3 ml was collected for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting, as well as deacetylase activity detection. The purified protein (1.25 μg) was subjected to 12% SDS-PAGE and then transferred to a nitrocellulose membrane (PALL, NY, USA) in blotting buffer (20 mM Tris-base, 150 mM glycine and 20% methanol, pH 8.3). After blocking with 10% non-fat dry milk in TBST buffer (10 mM Tris-HCl, pH 8.0, 150 mM NaCl and 0.