| Tuberculosis (TB) is a serious infectious disease. Mycobacterium tuberculosis is the main pathogen of TB. HIV and M.tuberculosis co-infection, the emergence of drug-resistant TB (especially multi drug-resistant (MDR) and extensively drug-resistant (XDR) TB) are the major challenges for the treatment of TB in world. Progress in TB prevention, treatment and control needs to find new molecules markers as diagnosis and vaccine. Proteomics is an important way to discover molecular markers at the protein level.In this study, whole cellular proteins of M.tuberculosis were extracted from the streptomycin(SM) resistant (SMr) clinical isolates 01108, the SM-sensitive (SMs) strains 01105 and H37Rv. The proteins were digested with trypsin and the peptides were separated and identified by isobaric tags for relative and absolute quantitation (iTRAQ) combined with Nano LC-MS/MS technology. The bioinformatics was used to analysis the functions of differential expressed proteins (DEP). Based on functional classification tree, the characters of DEP were analyzed including molecular weight (MW), the isoelectric point (pI), the enzyme classification and the functional classification. According to MW and pI, a virtual 2D gel of the DEP was drawn by Origin 8.1. Functional annotation clustering and signaling pathways were analyzed by WEGO and KEGG, respectively.194 and 146 DEP were identified and categorized in SMr strain compared with SMs strains and H37Rv, respectively.121 proteins were expressed differentially in SMr strain compared with both SMs strain and H37Rv, including seven proteins showing>1.20-fold increase or <0.55-fold decrease in SMr strain. The seven proteins were the thiol peroxidase (Rv1932), acyl carrier protein dehydrogenase (Rv0824c),30S ribosomal protein S15 (Rv2785c), acetone acid dehydrogenase E2 part (Rv2215), two-component transcriptional regulatory protein (Rv3133c) and unknown protein (Rv2466c and Rv2626c). The MW and pI of DEP were ranged from 7.63kDa (Rv1498A) to 326.22kDa (Rv2524c) and from 3.74 (Rv2244) to 12.48 (Rv2986c), respectively. More than 50% DEP were identified as protein protease. DEP were sorted by their functional category and no proteins in DEP belong to categories 4 (stable RNAs), categories 5 (insertion sequences and phages), categories 6 (PE/PPE), categories 8 (unknown), and categories 16 (conserved hypotheticals with an ortholog in M. bovis). Categories 7 (intermediary metabolism and respiration) comprised 36.1% and 32.4% of the total DEP in SMr strain compared with SMs strains and H37Rv, respectively.13 ribosome proteins were identified.According to the result of WEGO analysis, the catalytic activity function and binding function were the main molecular function annotations for DEP in SMr strain compared with both SMs strains and H37Rv. The DEP in SMr strain compared with SMs strains involved in 14 kinds of biological processes, which mainly include metabolism, cell processes, stress response and biological regulation.36.04% and 26.9% of genes take part in metabolic processes and cellular processes, respectively. The DEP in SMr strain compared with H37Rv involved in 13 biological processes, the metabolic processes and cellular processes were accounted for 34.02% and 26.9%, respectively. In this study, all identified proteins (785) belong to 72 signaling pathways with KEGG analysis, but only 9 signaling pathways were the significant (p<0.05), including citrate cycle, biosynthesis of unsaturated fatty acid and RNA degradation pathway.Our result showed that six proteins had a lower expression in SMr strains 01108 compared with both SMs strains 01105 and H37Rv, and just one had a higher expression in SMr strains 01108. The results suggest that seven proteins may be associated with virulence, and drug resistance of M. tuberculsois. It is necessary that further study will focus on seven proteins playing role in pathogenicity and resistance. |
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