Discussion The mycobacterial cell

envelope is a lipid-rich complex structure that surrounds the bacillus and is thought to play a critical role in the pathogenicity of Mycobacterium tuberculosis. Nearly 2.5% of the M. tuberculosis H37Rv proteome is predicted to consist of lipoproteins [17]. A large number of these find more mycobacterial lipoproteins have been suggested to be important components for the synthesis of the mycobacterial cell envelope, as well as for sensing processes, protection from stressful factors and host-pathogen interactions; nevertheless, the function and localization of a considerable number of putative lipoproteins remains yet unknown [41]. Lipoproteins are translocated across the cytoplasmic membrane and then anchored to either the periplasm or the outer membrane and have been suggested to play important roles related to virulence

because they are predicted to participate in intracellular transport, cell-wall metabolism, cell adhesion, signaling and protein degradation [42]. Rv0679c was initially classified as a hypothetical membrane protein of M. tuberculosis [9] and was later suggested to be a putative lipoprotein [29]. It is a 165-amino-acid-long protein with a theoretical TH-302 molecular mass of 16.6 kDa, whose function has not been fully characterized yet. In this study, PCR and RT-PCR techniques were used to examine the distribution of the Rv0679c gene in the MTC, as well as in mycobacteria other than tuberculosis (which included saprophytic and environmental species), with the aim of establishing a preliminary relationship between the presence of the protein encoding gene in a particular mycobacterial species and its virulence, considering that to develop a subunit antituberculous vaccine, it would be better to select peptides (more specifically 4��8C HABPs) from

M. tuberculosis proteins involved in host cell invasion that are exclusively present in MTC or in mycobacterium species related to invasive processes or causing disease, such as Rv0679c. The results of this study indicate that the gene encoding Rv0679c is present in the MTC, as shown by the PCR amplification of a 346-bp band from genomic DNA of M. tuberculosis H37Rv, M. tuberculosis H37Ra, M. africanum, M. bovis, M. bovis BCG and M. microti; but no amplification was detected in Mycobacterium spp. strains outside the complex. Nevertheless, it is worth noting that Rv0679c homologues have been recently reported in different Mycobacterium genomes (e.g. M. smegmatis, M. marinum and M. avium), which indicates that such primers are specific for the MTC strains assessed in this study. Furthermore, reverse transcription assays indicate that the gene is actively transcribed in M. tuberculosis H37Rv, M. tuberculosis H37Ra and M. africanum. Intriguingly, although expression of Rv0679c homologous protein in M. bovis BCG was described by Matsuba et al. [29], gene transcription was not detected in M. bovis nor in M.