Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mycobacteria contain an outer membrane composed of mycolic acids and a large variety of other lipids. Its protective function is an essential virulence factor of Mycobacterium tuberculosis. Only OmpA, which has numerous homologs in Gram-negative bacteria, is known to form channels in the outer membrane of M. tuberculosis so far. Rv1698 was predicted to be an outer membrane protein of unknown function. Expression of rv1698 restored the sensitivity to ampicillin and chloramphenicol of a Mycobacterium smegmatis mutant lacking the main porin MspA. Uptake experiments showed that Rv1698 partially complemented the permeability defect of the M. smegmatis porin mutant for glucose. These results indicated that Rv1698 provides an unspecific pore that can partially substitute for MspA. Lipid bilayer experiments demonstrated that purified Rv1698 is an integral membrane protein that indeed produces channels. The main single channel conductance is 4.5 +/- 0.3 nanosiemens in 1 M KCl. Zero current potential measurements revealed a weak preference for cations. Whole cell digestion of recombinant M. smegmatis with proteinase K showed that Rv1698 is surface-accessible. Taken together, these experiments demonstrated that Rv1698 is a channel protein that is likely involved in transport processes across the outer membrane of M. tuberculosis. Rv1698 has single homologs of unknown functions in Corynebacterineae and thus represents the first member of a new class of channel proteins specific for mycolic acid-containing outer membranes.
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PMID:Rv1698 of Mycobacterium tuberculosis represents a new class of channel-forming outer membrane proteins. 1843 14

The cell wall of mycobacteria includes an unusual outer membrane of extremely low permeability. While Escherichia coli uses more than 60 proteins to functionalize its outer membrane, only two mycobacterial outer membrane proteins (OMPs) are known. The porin MspA of Mycobacterium smegmatis provided the proof of principle that integral mycobacterial OMPs share the beta-barrel structure, the absence of hydrophobic alpha-helices and the presence of a signal peptide with OMPs of gram-negative bacteria. These properties were exploited in a multi-step bioinformatic approach to predict OMPs of M. tuberculosis. A secondary structure analysis was performed for 587 proteins of M. tuberculosis predicted to be exported. Scores were calculated for the beta-strand content and the amphiphilicity of the beta-strands. Reference OMPs of gram-negative bacteria defined threshold values for these parameters that were met by 144 proteins of unknown function of M. tuberculosis. Two of them were verified as OMPs by a novel two-step experimental approach. Rv1698 and Rv1973 were detected only in the total membrane fraction of M. bovis BCG in Western blot experiments, while proteinase K digestion of whole cells showed the surface accessibility of these proteins. These findings established that Rv1698 and Rv1973 are indeed localized in the outer membrane and tripled the number of known OMPs of M. tuberculosis. Significantly, these results provide evidence for the usefulness of the bioinformatic approach to predict mycobacterial OMPs and indicate that M. tuberculosis likely has many OMPs with beta-barrel structure. Our findings pave the way to identify the set of proteins which functionalize the outer membrane of M. tuberculosis.
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PMID:Identification of outer membrane proteins of Mycobacterium tuberculosis. 1843 72

Entry into host macrophages and evasion of intracellular destruction mechanisms, including phagosome-lysosome fusion, are critical elements of Mycobacterium tuberculosis (Mtb) pathogenesis. To achieve this, the Mtb genome encodes several proteins that modify host signaling pathways. PtpA, a low-molecular weight tyrosine phosphatase, is a secreted Mtb protein of unknown function. The lack of tyrosine kinases in the Mtb genome suggests that PtpA may modulate host tyrosine phosphorylated protein(s). We report that a genetic deletion of ptpA attenuates Mtb growth in human macrophages, and expression of PtpA-neutralizing antibodies simulated this effect. We identify VPS33B, a regulator of membrane fusion, as a PtpA substrate. VPS33B and PtpA colocalize in Mtb-infected human macrophages. PtpA secretion combined with active-phosphorylated VPS33B inhibited phagosome-lysosome fusion, a process arrested in Mtb infections. These results demonstrate that PtpA is essential for Mtb intracellular persistence and identify a key host regulatory pathway that is inactivated by Mtb.
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PMID:Mycobacterium tuberculosis virulence is mediated by PtpA dephosphorylation of human vacuolar protein sorting 33B. 1847 58

Johne's disease is a slowly developing intestinal disease, primarily of ruminants, caused by Mycobacterium avium subspecies paratuberculosis. The disease contributes to significant economic losses worldwide in agricultural industry. Analysis of bacterial proteomes isolated directly from infected animals can provide important information about the repertoire of proteins present during infection and disease progression. In this study, M. avium subspecies paratuberculosis has been extracted from Johne's disease-infected cattle and goat intestinal tissue sections in a manner compatible with direct 2-DE proteomic analysis for comparison with in vitro-cultured bacteria. M. avium subspecies paratuberculosis was harvested from the submucosa and mucosa of intestinal sections and enriched from macerated tissue by hypotonic lysis, sonication and centrifugation through a viscosity gradient. Subsequent comparison of the proteomes of the in vivo- and in vitro-derived bacteria identified a number of proteins that were differentially expressed. Among them, a number of hypothetical proteins of unknown function and a hypothetical fatty acyl dehydrogenase (FadE3_2) and 3-hydroxyacyl-CoA dehydrogenase, possibly important for in vivo metabolism, utilising the pathway for the beta-oxidation of fatty acids.
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PMID:The recovery of Mycobacterium avium subspecies paratuberculosis from the intestine of infected ruminants for proteomic evaluation. 1854 63

The direct repeat (DR) region is a singular locus of the Mycobacterium tuberculosis complex genome. This region consists of 36 bp repetitive sequences separated by non-repetitive unique spacer sequences. Around this region there are several genes coding for proteins of unknown function. To determine whether the M. smegmatis, M. avium, M. marinum and M. leprae genomes contain sequences and ORFs similar to those of the DR locus of the M. tuberculosis complex, we analysed the corresponding regions in these species. As a first step, some conserved genes that flank the DR genes [Rv2785c (rpsO), Rv2786c (ribF), Rv2790c (ltp1 ), Rv2793c (truB), Rv2800, Rv2825, Rv2828, Rv2831 (echA16 ), Rv2838 (rbfA) and Rv2845 (proS )] were used as markers to locate the corresponding orthologues in M. smegmatis, M. avium, M. marinum and M. leprae in silico. Most of these M. tuberculosis marker genes have highly similar orthologues located in the same order and orientation in the other mycobacteria. In contrast, no orthologues were found for ORFs Rv2801-Rv2824, suggesting that these genes are unique to M. tuberculosis within the genus Mycobacterium.We observed that in M. smegmatis and M. avium, Rv2800 and Rv2825 are adjacent. This observation was experimentally confirmed by PCR. In conclusion, as the DR locus and the ORFs around it are absent in M. smegmatis and M. avium and, as it is possible that these species are older than M. tuberculosis, we postulated that the DR locus was acquired by the M. tuberculosis complex species or by an ancestor bacterium.
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PMID:A fragment of 21 ORFs around the direct repeat (DR) region of Mycobacterium tuberculosis is absent from the other sequenced mycobacterial genomes: implications for the evolution of the DR region. 1862 72

The alternative sigma factor SigF of Mycobacterium tuberculosis has been characterized in detail as a general-stress, stationary-phase sigma factor involved in the virulence of the bacterium. While a homologous gene has been annotated in the genome of the fast-growing Mycobacterium smegmatis, little experimental evidence is available on the function of this gene. Here, we demonstrate that SigF of M. smegmatis is required for resistance to hydrogen peroxide, heat shock and acidic pH, but not for survival in human neutrophils. No difference in sensitivity to isoniazid was observed between the wild-type strain and the DeltasigF mutant, suggesting that SigF-mediated resistance to hydrogen peroxide was via a pathway independent of KatG or AhpC. RT-PCR and 5'-RACE (rapid amplification of cDNA ends) analyses showed that sigF of M. smegmatis was co-transcribed with rsbW (thought to encode an anti-sigma factor for SigF) and MSMEG_1802 (unknown function) and was expressed from two promoters, one upstream of MSMEG_1802 and the second upstream of rsbW. Analysis of transcriptional lacZ fusion constructs in the sigF-deletion background revealed that the MSMEG_1802 promoter was dependent on SigF for expression. Moreover, MSMEG_1802-lacZ was induced twofold upon entry into stationary phase, while exposure of exponentially growing cultures to various stress conditions (e.g. heat, cold, ethanol, hydrogen peroxide or different pH values) did not lead to induction of MSMEG_1802-lacZ. Expression of rsbW-lacZ was independent of SigF and remained constant throughout the growth cycle and under various stress conditions unless the bacteria were challenged with d-cycloserine.
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PMID:The alternative sigma factor SigF of Mycobacterium smegmatis is required for survival of heat shock, acidic pH and oxidative stress. 1875 12

Bioinformatic analyses have suggested that Mce proteins in diverse actinobacteria are components of complex ATP-binding cassette transporter systems, comprising more than eight distinct proteins. In Mycobacterium tuberculosis, these proteins are implicated in interactions of this deadly pathogen with its human host. Here, we provide direct evidence that the Mce4 system of Rhodococcus jostii RHA1 is a steroid uptake system. Transcriptional analyses indicate that the system is encoded by an 11-gene operon, up-regulated 4.0-fold during growth on cholesterol versus on pyruvate. Growth of RHA1 on cholesterol and uptake of radiolabeled cholesterol both required expression of genes in the mce4 operon encoding two permeases plus eight additional proteins of unknown function. Cholesterol uptake was ATP-dependent and exhibited Michaelis-Menten kinetics with a K(m) of 0.6 +/- 0.1 microm. This uptake system was also essential for growth of RHA1 on beta-sitosterol, 5-alpha-cholestanol, and 5-alpha-cholestanone. Bioinformatic analysis revealed that all mce4 loci in sequenced genomes are linked to steroid metabolism genes. Thus, we predict that all Mce4 systems are steroid transporters. The transport function of the Mce4 system is consistent with proposed roles of cholesterol and its metabolism in the pathogenesis of M. tuberculosis.
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PMID:The actinobacterial mce4 locus encodes a steroid transporter. 1895 93

Rhodococcus equi is one of the most important causes of mortality in foals between 1 and 6 months of age. Although rare, infection also occurs in a variety of other mammals including humans, often following immunosuppression of various causes. Secreted proteins are known to mediate important pathogen-host interactions and consequently are favored candidates for vaccine development as they are the most easily accessible microbial antigens to the immune system. Here, we describe the results of a proteomic analysis based on SDS-PAGE, immunoblot and mass spectrometry, which was carried out aiming the identification of secreted proteins that are differently expressed at 30 degrees C versus 37 degrees C and at mid-exponential versus early-stationary growth phase and antigenic proteins from R. equi ATCC 33701. A total of 48 proteins was identified regardless of growth conditions. The cholesterol oxidase ChoE appears to be the major secretory protein. Moreover, four proteins revealed high homologies with the mycolyl transferases of the Ag85 complex from Mycobacterium tuberculosis. The sequence analysis predicted that 24 proteins are transported by a signal peptide-dependent pathway. Moreover, five antigenic proteins of R. equi were identified by immunoblot, including a novel strongly immunoreactive protein of unknown function. In conclusion, the elucidation of the secretome of R. equi identified several proteins with different biological functions and a new candidate for developing vaccines against R. equi infection in horse.
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PMID:Proteomic analysis and immunogenicity of secreted proteins from Rhodococcus equi ATCC 33701. 1901 79

Comparative genomics with Staphylococcus aureus suggested the existence of a regulatory system governing beta-lactamase (BlaC) production in Mycobacterium tuberculosis. The crystal structure of Rv1846c, a winged helix regulator of previously unknown function, was solved thus revealing strong similarity to the BlaI and MecI repressors of S. aureus, which both respond to beta-lactam treatment. Using chromatin immunoprecipitation and hybridization to microarrays (ChIP-on-chip), the Rv1846c regulon was shown to comprise five separate genomic loci. Two of these mediate responses and resistance to beta-lactam antibiotics (rv1845c, rv1846c-rv1847; blaC-sigC); two encode membrane proteins of unknown function (rv1456c, rv3921c) while the last codes for ATP synthase (rv1303-atpBEFHAGDC-rv1312). The ChIP-on-chip findings were confirmed independently using electrophoretic mobility shift assays, DNAse footprinting and transcript analysis leading to Rv1846c being renamed BlaI. When cells were treated with beta-lactams, BlaI was released from its operator sites causing derepression of the regulon and upregulation of ATP synthase transcription. The existence of a potential regulatory loop between cell wall integrity and ATP production was previously unknown.
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PMID:Genome-wide regulon and crystal structure of BlaI (Rv1846c) from Mycobacterium tuberculosis. 1915 33

Recent efforts have underlined the role of serine/threonine protein kinases in growth, pathogenesis, and cell wall metabolism in Mycobacterium tuberculosis. Although most kinases have been investigated for their physiological roles, little information is available regarding how serine/threonine protein kinase-dependent phosphorylation regulates the activity of kinase substrates. Herein, we focused on M. tuberculosis Rv2175c, a protein of unknown function, conserved in actinomycetes, and recently identified as a substrate of the PknL kinase. We solved the solution structure of Rv2175c by multidimensional NMR and demonstrated that it possesses an original winged helix-turn-helix motif, indicative of a DNA-binding protein. The DNA-binding activity of Rv2175c was subsequently confirmed by fluorescence anisotropy, as well as in electrophoretic mobility shift assays. Mass spectrometry analyses using a combination of MALDI-TOF and LC-ESI/MS/MS identified Thr(9) as the unique phosphoacceptor. This was further supported by complete loss of PknL-dependent phosphorylation of an Rv2175c_T9A mutant. Importantly, the DNA-binding activity was completely abrogated in a Rv2175c_T9D mutant, designed to mimic constitutive phosphorylation, but not in a mutant lacking the first 13 residues. This implies that the function of the N-terminal extension is to provide a phosphoacceptor (Thr(9)), which, following phosphorylation, negatively regulates the Rv2175c DNA-binding activity. Interestingly, the N-terminal disordered extension, which bears the phosphoacceptor, was found to be restricted to members of the M. tuberculosis complex, thus suggesting the existence of an original mechanism that appears to be unique to the M. tuberculosis complex.
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PMID:The Mycobacterium tuberculosis Ser/Thr kinase substrate Rv2175c is a DNA-binding protein regulated by phosphorylation. 1945 63


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