Definition of novel cell envelope associated proteins in Triton X-114 extracts of Mycobacterium tuberculosis H37Rv

In total, 1417 different proteins were identified. In silico analysis of the identified proteins revealed that 248 proteins had at least one predicted trans-membrane region. Also, 64 of the identified proteins were predicted lipoproteins, and 54 proteins were predicted as outer membrane proteins. Three-hundred-and-ninety-five of the observed proteins, including 91 integral membrane proteins were described for the first time. Comparison of abundance levels of the identified proteins was performed using the exponentially modified protein abundance index (emPAI) which takes into account the number of the observable peptides to the number of experimentally observed peptide ions for a given protein. The outcome showed that among the membrane-and membrane-associated proteins several proteins are present with high relative abundance. Further, a close examination of the lipoprotein LpqG (Rv3623) which is only detected in the membrane fractions of M. tuberculosis but not in M. bovis, revealed that the homologous gene in M. bovis lack the signal peptide and lipobox motif, suggesting impaired export to the membrane.Altogether, we have identified a substantial proportion of membrane- and membrane-associated proteins of M. tuberculosis H37Rv, compared the relative abundance of the identified proteins and also revealed subtle differences between the different members of the M. tuberculosis complex.Tuberculosis is an airborne infection caused by Mycobacterium tuberculosis. It is estimated that one-third of the world's population is latently infected with M. tuberculosis, and that each year about three million people die of this disease. The emergence of drug-resistant stains is further escalating the threat to public health (WHO, 2003). In spite of global research efforts, mechanisms underlying pathogenesis, virulence and persistence of M. tuberculosis infection remain poorly understood [1].M. tuberculosis is a facultative intracellular pathogen that resides within the host macrop