Another interesting group of proteins that are associated with the Selleck Opaganib membrane is lipoproteins. These are proteins translocated to the cell membrane and retained there by post-translational lipid modification. They are functionally diverse, and are suggested to be involved in host-pathogen interactions [28, 29]. They are also interesting with respect to development of serodiagnostic tests for detection

of TB due to their strong immunogenicity [30, 31]. Lipoproteins represent a subgroup of secreted proteins characterized by the presence of a lipobox. The lipobox motif is located in the distal C-terminal part of the N-terminal signal peptide [32]. This motif functions as a recognition signal for lipid modification, which is made on the conserved and essential cysteine residue. Precursor lipoproteins are mainly translocated in a Sec-dependent manner across the plasma membrane and are RAD001 subsequently

modified [33]. The proteins identified in this study were analysed by PROSITE for prediction of lipoproteins http://​au.​expasy.​org/​prosite/​. Seventy-six of them were predicted as potential lipoproteins, based on the presence of a cleavable signal peptide and signal peptidase II recognition motif. Sixty six of all the lipoproteins were common for both strains, while 7 lipoproteins were only observed in M. tuberculosis H3Ra and 3 lipoproteins only observed in M. tuberculosis H37Rv (Additional file 4). Estimation of relative abundance Using MaxQuant

software that provide quantitative ADP ribosylation factor information about proteins and peptides using the spectra generated during the LC runs the relative abundance of each protein observed in both M. tuberculosis H37Rv and M. tuberculosis H37Ra were examined after normalization. Our data showed that most of the proteins identified in both strains had similar relative abundance. Using Pearson’s method for correlation, the relative abundance of proteins observed in the two strains were significantly correlated with a correlation coefficient of 0.887 (p < 0.001), and R2 = 0.78 (Figure 2). However, there were some proteins that had different relative abundance between the two strains. To ensure the relative protein abundance for these proteins were real and not due to technical error margins, we only focused on the ones with a 5 fold difference or higher. To this end, there were 121 proteins from both strains that belonged to different functional groups (Additional file 5). In order to reduce the amount of data required to be analysed, and due to the anticipated important biological role of membrane- and membrane-associated proteins, we chose to focus only on membrane- and lipoproteins. This further reduced the number of proteins to only 19 and 10 proteins in M. tuberculosis H37Rv and M. tuberculosis H37Ra, respectively (Table 1). Among the proteins observed with a 5 fold or higher relative abundance in M.