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Directed shotgun proteomics guided by RNA-Seq identifies a complete expressed prokaryotic proteome

ABSTRACT: Prokaryotes are, due to their moderate complexity, particularly amenable to the comprehensive identification of the protein repertoire expressed under different conditions. We applied a generic strategy to identify a complete expressed prokaryotic proteome, which is based on the analysis of RNA and proteins extracted from matched samples. Saturated transcriptome profiling by RNA-seq provided an endpoint estimate of the protein-coding genes expressed under two conditions which mimic the interaction of Bartonella henselae with its mammalian host. Directed shotgun proteomics experiments were carried out on four subcellular fractions. By specifically targeting proteins which are short, basic, low abundant and membrane localized, we could eliminate their initial under-representation compared to the estimated endpoint. A total of 1,250 proteins were identified with an estimated false discovery rate below 1%. This represents 85% of all distinct annotated proteins and around 90% of the expressed protein-coding genes. Genes, whose transcripts were detected, but not their corresponding protein products, were found highly enriched in several genomic islands. Additionally, genes that lacked an ortholog and a functional annotation were not detected at the protein level, and possibly include over-predicted genes in genome annotations. Furthermore, a dramatic membrane proteome re-organization was observed including differential regulation of autotransporters, adhesins and hemin binding proteins. Particularly noteworthy was the complete membrane proteome coverage which included expression of all members of the VirB/D4 type IV secretion system, a key virulence factor.

ORGANISM(S): Bartonella henselae

PROVIDER: GSE44564 | GEO | 2013/04/23

SECONDARY ACCESSION(S): PRJNA190078

REPOSITORIES: GEO

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Project description:Understanding the immune response to tuberculosis requires greater knowledge of humoral responses. To characterize antibody targets and the effect of disease parameters on target recognition, we developed a systems immunology approach that integrated detection of antibodies against the entire Mycobacterium tuberculosis proteome, bacterial metabolic and regulatory pathway information, and patient data. Probing ~4,000 M. tuberculosis proteins with sera from >500 suspected tuberculosis patients worldwide revealed that antibody responses recognized ~10% of the bacterial proteome. This result defines the immunoproteome of M. tuberculosis, which is rich in membrane-associated and extracellular proteins. Most serum reactivity during active tuberculosis focused onto ~0.5% of the proteome. Within this pool, which is selectively enriched for extracellular proteins (but not for membrane-associated proteins), relative target preference varied among patients. The shift in relative M. tuberculosis protein reactivity observed with active tuberculosis defines the evolution of the humoral immune response during M. tuberculosis infection and disease. Peripheral blood was collected from prospectively enrolled TB suspects among subjects seeking care for pulmonary symptoms at clinics associated with national TB control programs in 11 countries. M. tuberculosis proteome microarrays representing 4099 bacterial protein spots were probed with sera from 561 TB suspects. Based on the final diagnosis, they belonged to two classes: TB (n=254) and Non-TB Disease (n=307). In addition, healthy individuals negative to Latent TB Infection (LTBI neg, n=64) were also tested (negative control sera). Each serum was tested with a single array and no replicate experiments were performed. The reactivity of a serum to an M. tuberculosis protein (reactivity call) was defined based on the distribution of negative control sera intensity for that protein using Z-statistics. Based on the distribution of reactivity calls, 27 outlier samples reacting with more than 20 proteins were excluded from further analysis. The association of reactivity calls of each protein with TB/NTBD status of TB suspects was determined by estimating odds ratio and 95% confidence interval.

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Directed shotgun proteomics guided by RNA-Seq identifies a complete expressed prokaryotic proteome

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