Comprehensive analysis of exported proteins from Mycobacterium tuberculosis H37Rv. Proteomics 7:1702–1718

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: 1) 2D-PAGE combined with MALDI-TOF MS and 2) liquid chromatography 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 recognition and cleavage of signal peptides in mycobacteria. A larg