Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutations causing rifampin resistance in vegetative cells of Bacillus subtilis 168 have thus far been mapped to a rather restricted set of alterations at either Q469 or H482 within cluster I of the rpoB gene encoding the beta subunit of RNA polymerase. In this study, we demonstrated that spores of B. subtilis 168 exhibit a spectrum of spontaneous rifampin resistance mutations distinct from that of vegetative cells. In addition to the rpoB mutations Q469K, Q469R, and H482Y previously characterized in vegetative cells, we isolated a new mutation of rpoB, H482R, from vegetative cells. Additional new rifampin resistance mutations arising from spores were detected at A478N and most frequently at S487L. The S487L change is the predominant change found in rpoB mutations sequenced from rifampin-resistant clinical isolates of Mycobacterium tuberculosis. The observations are discussed in terms of the underlying differences of the DNA environment within dormant cells and vegetatively growing cells.
...
PMID:The spectrum of spontaneous rifampin resistance mutations in the rpoB gene of Bacillus subtilis 168 spores differs from that of vegetative cells and resembles that of Mycobacterium tuberculosis. 1216 22

The extracytoplasmic function (ECF) sigma factor sigma(R) is a global regulator of redox homeostasis in the antibiotic-producing bacterium Streptomyces coelicolor, with a similar role in other actinomycetes such as Mycobacterium tuberculosis. Normally maintained in an inactive state by its bound anti-sigma factor RsrA, sigma(R) dissociates in response to intracellular disulphide-stress to direct core RNA polymerase to transcribe genes, such as trxBA and trxC that encode the enzymes of the thioredoxin disulphide reductase pathway, that re-establish redox homeostasis. Little is known about where RsrA binds on sigma(R) or how it suppresses sigma(R)-dependent transcriptional activity. Using a combination of proteolysis, surface-enhanced laser desorption ionisation mass spectrometry and pull-down assays we identify an N-terminal, approximately 10kDa domain (sigma(RN)) that encompasses region 2 of sigma(R) that represents the major RsrA binding site. We show that sigma(RN) inhibits transcription by an unrelated sigma factor and that this inhibition is relieved by RsrA binding, reaffirming that region 2 is involved in binding to core RNA polymerase but also demonstrating that the likely mechanism by which RsrA inhibits sigma(R) activity is by blocking this association. We also report the 2.4A resolution crystal structure of sigma(RN) that reveals extensive structural conservation with the equivalent region of sigma(70) from Escherichia coli as well as with the cyclin-box, a domain-fold found in the eukaryotic proteins TFIIB and cyclin A. sigma(RN) has a propensity to aggregate, due to steric complementarity of oppositely charged surfaces on the domain, but this is inhibited by RsrA, an observation that suggests a possible mode of action for RsrA which we compare to other well-studied sigma factor-anti-sigma factor systems.
...
PMID:Identification and structure of the anti-sigma factor-binding domain of the disulphide-stress regulated sigma factor sigma(R) from Streptomyces coelicolor. 1238 17

The use of rifamycins is limited by drug interactions in human immunodeficiency virus (HIV)-infected persons who are receiving highly active antiretroviral therapy (HAART). During a tuberculosis (TB) outbreak at a prison housing HIV-infected inmates, rifabutin was used to treat 238 men (13 case patients and 225 contacts). Steady-state peak plasma rifabutin concentrations were obtained after rifabutin dosages were adjusted for men receiving single-interacting HAART (with either 1 protease inhibitor [PI] or efavirenz), multi-interacting HAART (with either 2 PIs or > or =1 PI with efavirenz), and for noninteracting HAART (>1 nucleoside reverse-transcriptase inhibitor or no HAART) without rifabutin dose adjustments. Low rifabutin concentrations occurred in 9% of those receiving noninteracting HAART, compared with 19% of those receiving single-interacting and 29% of those receiving multi-interacting HAART (chi2, 3.76; P=.05). Of 225 contacts treated with rifabutin-pyrazinamide, 158 (70%) completed treatment while incarcerated. Rifabutin-pyrazinamide therapy was difficult to implement, because of the need for dosage adjustments and expert clinical management.
...
PMID:Drug-drug interactions in inmates treated for human immunodeficiency virus and Mycobacterium tuberculosis infection or disease: an institutional tuberculosis outbreak. 1238 45

Transcriptional regulation of genes involved in the biosynthesis of cell wall lipids of Mycobacterium tuberculosis is poorly understood. The gene encoding mycocerosic acid synthase (mas) and fadD28, an adjoining acyl coenzyme A synthase gene, involved in the production of a virulence factor, dimycocerosyl phthiocerol, were cloned from Mycobacterium bovis BCG, and their promoters were analyzed. The putative promoters were fused to the xylE reporter gene, and its expression was measured in Escherichia coli, Mycobacterium smegmatis, and M. bovis BCG. In E. coli, the fadD28 promoter was not functional but the mas promoter was functional. Both fadD28 and mas promoters were functional in M. smegmatis, at approximately two- and sixfold-higher levels, respectively, than the BCG hsp60 promoter. In M. bovis BCG, the fadD28 and mas promoters were functional at three- and fivefold-higher levels, respectively, than the hsp60 promoter. Primer extension analyses identified transcriptional start points 60 and 182 bp upstream of the translational start codons of fadD28 and mas, respectively. Both promoters contain sequences similar to the canonical -10 and -35 hexamers recognized by the sigma(70) subunit of RNA polymerase. Deletions of the upstream regions of both genes indicated that 324 bp of the fadD28 and 228 bp of the mas were essential for promoter activity. Further analysis of the mas promoter showed that a 213-bp region 581 bp upstream of the mas promoter acted as a putative transcriptional enhancer, promoting high-level expression of the mas gene when present in either direction. This represents the identification of a rare example of an enhancer-like element in mycobacteria.
...
PMID:Regulation of expression of mas and fadD28, two genes involved in production of dimycocerosyl phthiocerol, a virulence factor of Mycobacterium tuberculosis. 1244 29

Multidrug resistance among new cases of tuberculosis (TB) is increasingly becoming a significant problem in countries with a high prevalence of TB and with inadequate therapies for TB. Rifampin resistance is widely used as a marker for multidrug-resistant (MDR) TB; therefore, a new approach to the retrospective measurement of rifampin resistance without the need of a viable culture has been introduced. In many developing countries culture is unavailable and diagnosis relies on clinical manifestations and the results of Ziehl-Neelsen staining of sputum smears. We determined rifampin resistance directly with DNA extracts from Ziehl-Neelsen-stained slides by identification of mutations in the rpoB gene using reverse line blot hybridization and DNA sequencing. Analysis of the rpoB gene revealed that samples containing rifampin-resistant Mycobacterium tuberculosis carried altered codons representing amino acid positions 516, 526, and 531 of the RNA polymerase. Although the sensitivities of both methods were equal (84%), sequencing of the rpoB gene was more accurate in identifying mutations in the core region of the rpoB gene. Sequence analysis of the rpoB gene in extracts from Ziehl-Neelsen-stained slides may be used to quantify more precisely the magnitude of MDR TB and, more importantly, provide information on trends in the development of resistance on a global scale. The nature of rifampin resistance and the genotype can be determined by analysis of Ziehl-Neelsen-stained slides in a laboratory equipped for sequencing and spoligotyping without the need to ship biohazardous materials.
...
PMID:Use of DNA extracts from Ziehl-Neelsen-stained slides for molecular detection of rifampin resistance and spoligotyping of Mycobacterium tuberculosis. 1262 36

This study describes the development of a novel thiocationic (OBEHYTOP) lipid-based formulation of phosphorothioate antisense oligonucleotides (PAOs) showing inhibitory activity against mycobacterium tuberculosis (mTB) as measured by an in vitro BACTEC 460TB assay. PAOs were designed based on sequences complementary to essential regions of the mycobacterial genome from published nucleic acid databases in GenBank. These included the superoxide dismutase sod A gene (TBS3), catalase-peroxidase katG gene (TBK1, TBK10), RNA polymerase beta-subunit rpo B gene (TBR5) and diaminopimelate decarboxylase lys A gene (TBL5). The effect of PAOs (TBS3, K1, K10, R5 and L5) alone on mTB was not significant compared with the no-drug control over a period of exposure of 150 h (ranges of -11.8 to +23.58% at 72 h; 15.26 to +25.82% at 96 h and -5.51 to +24.00% at 150 h). Liposomal formulations (10:5:2 OBEHYTOP:oleic acid:vitamin D3) of PAOs resulted in statistically significant (p < 0.05 in all cases) inhibition (ranges of -51.45 to -63.00% at 72 h; -56.75 to -67.96% at 96 h; -51.45 to -60.26% at 150 h) compared with PAOs alone, thiocationic liposomal control and liposomal components. Positive controls of streptomycin and isoniazid used at their minimum inhibitory concentrations of 2.00 and 0.10 microM, respectively, resulted in average % inhibition values of -94% and -97.36%, respectively, indicating that these thiocationic lipid-formulated PAOs showed inhibitory activity directed against mTB in vitro.
...
PMID:A novel thiocationic liposomal formulation of antisense oligonucleotides with activity against Mycobacterium tuberculosis. 1275 11

In a systematic approach to understand the transcriptional machinery of mycobacteria, we had previously isolated and characterized mycobacterial promoter regions. In this study, we have investigated molecular interactions between mycobacterial RNA polymerase holoenzyme, reconstituted with different sigma subunits and the promoter element of the Mycobacterium tuberculosis gene pknH (Rv1266c), a representative of promoters belonging to the 'extended -10' class. In vitro transcription assays using the pknH promoter and reconstituted RNA polymerase holoenzyme demonstrated that transcription from the pknH promoter is specifically initiated by sigmaA, the principal sigma factor of mycobacteria. DNase I protection assay and deletion studies with the pknH promoter revealed that the minimal region required for optimal transcription carries the sequence from position -37 to position +6. Moreover, mutation in the TGN motif of the pknH promoter resulted in the loss of >75% of its activity. Binding of RNA polymerase with wild-type promoter as well as its TG- mutant revealed that the TGN motif is required for the transition from a close complex into an open complex. Further, it was observed that the presence of the TGN motif reduces the thermal energy required for the conversion of a close complex into an open complex, necessary for initiation of transcription.
...
PMID:Role of 5'-TGN-3' motif in the interaction of mycobacterial RNA polymerase with a promoter of 'extended -10' class. 1290 24

The variation in sequence and length in the C-terminal region among members of the unique PE (Pro-Glu) and PPE (Pro-Pro-Glu) protein families of Mycobacterium tuberculosis is a likely source of antigenic variation, giving rise to the speculation that these protein families could be immunologically important. Based on in silico analysis, we selected a hypothetical open reading frame (ORF) encoding a protein belonging to the PPE family and having epitopes with predictably higher antigenic indexes. Reverse transcriptase PCR using total RNA extracted from in vitro-cultured M. tuberculosis H37Rv generated an mRNA product corresponding to this gene, indicating the expression of this ORF (Rv2430c) at the mRNA level. Recombinant protein expressed in Escherichia coli was used to screen the sera of M. tuberculosis-infected patients, as well as those of clinically healthy controls (n = 10), by enzyme-linked immunosorbent assay. The panel of patient sera comprised sera from fresh infection cases (category 1; n = 32), patients with relapsed tuberculosis (category 2; n = 30), and extrapulmonary cases (category 3; n = 30). Category 2 and 3 sera had strong antibody responses to the PPE antigen, equal to or higher than those to other well-known antigens, such as Hsp10 or purified protein derivative (PPD). However, a higher percentage of patients belonging to category 1, as opposed to clinically healthy controls, showed stronger antibody response against the PPE protein when probed with anti-immunoglobulin M (IgM) (71 versus 37.5%) or anti-IgG (62.5 versus 28.12%). Our results reveal that this PPE ORF induces a strong B-cell response compared to that generated by M. tuberculosis Hsp10 or PPD, pointing to the immunodominant nature of the protein.
...
PMID:PPE antigen Rv2430c of Mycobacterium tuberculosis induces a strong B-cell response. 1457 53

In this study, the expression of the Mycobacterium tuberculosis PE, PE_polimorphic GC-rich sequences (PGRS) gene family encoding approximately 99 glycine-rich proteins was assayed by reverse-transcriptase polymerase chain reaction (RT-PCR) in M. tuberculosis H37Rv, Mycobacterium canettii and two clinical isolates of M. tuberculosis. Restriction analyses and sequencing of the RT-PCR products showed that all the strains expressed the PE Rv1172c gene while the PE_PGRS Rv3652 gene was only expressed by one of the M. tuberculosis clinical isolates, and the PE_PGRS Rv0578c was not expressed by M. canettii. It was also determined that the PE_PGRS Rv0278c and Rv0279c were not expressed by any of the studied strains. The data presented in this report show that the PE, PE_PGRS genes are differentially expressed in M. tuberculosis strains during in vitro growth. These findings suggest that PE, PE_PGRS genes may play a role in protein variation between M. tuberculosis strains.
...
PMID:Differential expression of PE and PE_PGRS genes in Mycobacterium tuberculosis strains. 1458

We report the crystal structure of N-utilizing substance A protein (NusA) from Thermotoga maritima (TmNusA), a protein involved in transcriptional pausing, termination, and antitermination. TmNusA has an elongated rod-shaped structure consisting of an N-terminal domain (NTD, residues 1-132) and three RNA binding domains (RBD). The NTD consists of two subdomains, the globular head and the helical body domains, that comprise a unique three-dimensional structure that may be important for interacting with RNA polymerase. The globular head domain possesses a high content of negatively charged residues that may interact with the positively charged flaplike domain of RNA polymerase. The helical body domain is composed of a three-helix bundle that forms a hydrophobic core with the aid of two neighboring beta-strands. This domain shows structural similarity with one of the helical domains of sigma(70) factor from Escherichia coli. One side of the molecular surface shows positive electrostatic potential suitable for nonspecific RNA interaction. The RBD is composed of one S1 domain and two K-homology (KH) domains forming an elongated RNA binding surface. Structural comparison between TmNusA and Mycobacterium tuberculosis NusA reveals a possible hinge motion between NTD and RBD. In addition, a functional implication of the NTD in its interaction with RNA polymerase is discussed.
...
PMID:Crystal structure of NusA from Thermotoga maritima and functional implication of the N-terminal domain. 1462 88


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---