Comprehensive analysis of exported proteins from Mycobacterium tuberculosis H37Rv

Abstract

Proteins secreted by Mycobacterium tuberculosis play an essential role in the pathogenesis of tuberculosis. The culture filtrates of M. tuberculosis H37Rv made by Sadamu Nagai (Japan), are considerably enriched for secreted proteins compared to other culture filtrates. Complementary approaches were used to identify the secreted proteins in these culture filtrates: (i) 2-DE combined with MALDI-TOF MS and (ii) LC coupled MS/MS. Peptides derived from a total of 257 proteins were identified of which 144 were identified by more than one peptide. Several members of the immunologically important early secretory antigenic target-6 (ESAT-6) family of proteins were found to be major components. The majority of the identified proteins, 159 (62%), were predicted to be exported through the general secretory pathway. We experimentally verified that the signal peptides, which mediate translocation through the cell membrane, had been removed in 41 of the identified proteins, and in 35 of those, there was an AXA motif N-terminally to the cleavage site, showing that this motif is important for the recognition and cleavage of signal peptides in mycobacteria. A large fraction of the secreted proteins were unknown, suggesting that we have mapped an unexplored part of the exported proteome of M. tuberculosis. complement.

Mycobacterium tuberculosis acquires iron by cell-surface sequestration and internalization of human holo-transferrin

“…This observation is in accordance with previous results where it has been identified as a 43.6-kDa culture filtrate protein of M. bovis 41 and as a membrane-associated protein in M.tb H37Rv [42][43][44][45] . The presence of GAPDH and other glycolytic proteins on the surface of several prokaryotes and eukaryotic cells, despite the lack of a distinct secretory signal, has been referred to as 'nonclassical secretion' 46,47 and a bioinformaticsbased analysis of M.tb GAPDH failed to predict any secretion via the sec-dependent or twin arginine translocation system 41 .…”

Glycolytic and Non-glycolytic Functions of Mycobacterium tuberculosis Fructose-1,6-bisphosphate Aldolase, an Essential Enzyme Produced by Replicating and Non-replicating Bacilli

“…95% of the M. tuberculosis H37Ra bacilli grown as an undisturbed surface pellicle in Sauton medium were found in the R region, suggesting that the majority of the bacterial population had FBA-tb present on the cell surface. The finding of FBA-tb at the cell surface and in culture filtrates, although surprising in view of the apparent lack of secretion signals in the protein and its glycolytic/gluconeogenetic function, is consistent with the reported surface exposure of class II FBP aldolases from several other bacterial and fungal pathogens (40, 50 -54) and earlier proteomics observations on M. tuberculosis (17,55,56).…”

Immunoproteomic Identification of Human T Cell Antigens of Mycobacterium tuberculosis That Differentiate Healthy Contacts from Tuberculosis Patients

“…Later, many studies used twodimensional (2D) PAGE combined with sensitive mass spectrometric methods for identification of proteins. The above mentioned approaches have identified nearly 300 culture filtrate proteins (11)(12)(13).…”