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)

Sigma factors are transcription-regulatory proteins that bind to RNA polymerase and facilitate promoter recognition. The so-called extracytoplasmic function sigma factors help a bacterium to respond to environmental conditions. Mycobacterium tuberculosis SigC (sigmaC) is an extracytoplasmic sigma factor that is essential for lethality in a mouse model of infection and is conserved in all pathogenic mycobacterial species. This protein consists of two domains that are connected by an approximately 25-amino-acid linker. The N-terminal domain contains the sigma2 DNA-binding motif, whereas the sigma4 motif is located in the C-terminal domain. Native sigmaC did not yield diffraction-quality crystals. However, two of its domains have been cloned, expressed and crystallized: sigmaC2 (12.3 kDa) and sigmaC4 (7.5 kDa). The sigmaC2 crystals belong to the hexagonal space group P6(1), with unit-cell parameters a = b = 85.28, c = 79.63 A, and native X-ray diffraction data were collected from this domain to 2.7 A on an in-house X-ray home source. The sigmaC4 crystals belong to the cubic space group F23, with unit-cell parameters a = b = c = 161.21 A. X-ray diffraction data were collected from this domain to 3.1 A, also on an in-house X-ray source.
...
PMID:Crystallization and preliminary X-ray diffraction studies of two domains of a bilobed extra-cytoplasmic function sigma factor SigC from Mycobacterium tuberculosis. 1651 Nov 56

Nucleotide changes in catalase peroxidase (Kat G) gene and gene encoding the beta subunit of RNA polymerase (rpo B), responsible for isoniazid and rifampicin drug resistance were determined in the clinical isolates of Mycobacterium tuberculosis by PCR-RFLP, Line probe assay and DNA sequencing. PCR-RFLP test was performed by HapII cleavage of an amplified fragment of Kat G gene to detect the transversion 315AGC-->ACC(Ser-->Thr) which is associated with INH drug resistance. The Line probe assay kit was evaluated to detect the mutation in 81bp RMP resistance determining region of rpo B gene associated with RMP drug resistance. These results were validated by DNA sequencing and drug susceptibility test. Kat G S 315 T mutation was found in 74.19% strains of M. tuberculosis from Delhi. This mutation was not found in any of the susceptible strains tested. The line probe assay kit and DNA sequencing identified 18 isolates as RMP resistant with specific mutation, while one of the RMP resistant strain was identified as RMP susceptible, with a concordance of 94.73% with the phenotypic drug susceptibility result. Majority (8 of 19, 42.1%) of resistant isolates involved base changes at codon 531 of rpo B gene. Both PCR-RFLP and Line probe assay test can be used in many of the clinical microbiology laboratories for early detection of isoniazid and rifampicin drug resistance in clinical isolates of M. tuberculosis.
...
PMID:Molecular characterization of mutation associated with rifampicin and isoniazid resistance in Mycobacterium tuberculosis isolates. 1687 43

RNA polymerase (RNAP) is a well-validated target for the development of antibacterial and antituberculosis agents. Because the purification of large quantities of native RNA polymerase from pathogenic mycobacteria is hazardous and cumbersome, the primary screening was carried out using Escherichia coli RNAP. The authors have developed a high-throughput screening (HTS) assay to screen for novel inhibitors of RNAP. In this assay, a fluorescent analog of UTP, gamma-amino naphthalene sulfonic acid (gamma-AmNS) UTP, was used as one of the nucleotide substrates. Incorporation of UMP in RNA results in the release of gamma-AmNS-PPi, which has higher intrinsic fluorescence than (gamma-AmNS) UTP. The assay was optimized in a 384-well format and used to screen 670,000 compounds at a concentration of 10 microM. About 0.1% of the compounds showed more than 60% inhibition in the primary HTS. All the primary actives tested for dose response using the same assay had an EC(50) below 100 microM. Eighty percent of the primary HTS actives obtained using E. coli RNAP showed comparable activity against Mycobacterium smegmatis RNAP in the conventional radioactive assay. Activity of hits selected for the hit-to-lead optimization was also confirmed against Mycobacterium bovis RNAP which has >99% sequence identity with Mycobacterium tuberculosis RNAP subunits.
...
PMID:High-throughput screening of RNA polymerase inhibitors using a fluorescent UTP analog. 1702 9

Human tuberculosis is still one of the most frequent causes of death worldwide. Despite the implementation of therapeutic regimes combining four drugs, the rise of resistant and multidrug-resistant Mycobacterium tuberculosis strains has compromised their efficacy. Two of the most effective anti-tubercular drugs in use, rifampicin and isoniazid, have been closely studied due to their therapeutic importance. These studies have led to the identification of the genes involved in resistance mechanisms and of those encoding the molecular targets for these drugs. Rifampicin is an inhibitor of the beta-subunit of the RNA polymerase of prokaryotes, including M. tuberculosis. Resistance to rifampicin is mediated by mutations clustered in a small region of the rpoB gene. A fraction of resistant strains showed no mutations in rpoB, suggesting that other mechanisms of resistance, possibly efflux pumps, may exist. Isoniazid is a pro-drug activated by KatG, a catalase-peroxidase. Mutations in katG, the most commonly found in M. tuberculosis clinical isolates, give high levels of resistance. In spite of this, the molecular target for isoniazid is InhA, an enoyl-ACP-reductase involved in the biosynthesis of mycolic acids. Other mutations causing resistance to isoniazid have been mapped to ndh, a gene encoding the NADH dehydrogenase.
...
PMID:[Mechanisms of action of and resistance to rifampicin and isoniazid in Mycobacterium tuberculosis: new information on old friends]. 1703 59

Mycobacterium tuberculosis is a remarkable pathogen capable of adapting and surviving in various harsh conditions. Correct gene expression regulation is essential for the success of this process. The reversible association of different sigma factors is a common mechanism for reprogramming bacterial RNA polymerase and modulating the transcription of numerous genes. Thirteen putative sigma factors are encoded in the M. tuberculosis genome, several being important for virulence. Here, we analyse the latest information available on mycobacterial sigma factors and discuss their roles in the physiology and virulence of M. tuberculosis.
...
PMID:The sigma factors of Mycobacterium tuberculosis. 1706 87

A previously optimized Escherichia coli two-plasmid system was used to identify Mycobacterium tuberculosis promoters recognized by RNA polymerase containing the M. tuberculosis stress response sigma factor sigma(F). The method allowed the identification of five new sigma(F)-dependent promoters. Transcriptional start points of the promoters were determined by high-resolution S1-nuclease mapping using RNA prepared from E. coli containing the two-plasmid system. The promoters were confirmed by an in vitro transcription assay. The Mycobacterium smegmatis and Mycobacterium tuberculosis core RNA polymerases, after complementation with sigma(F), were able to recognize all the five promoters. All the promoters contained sequences highly similar to the sequence of the previously identified M. tuberculosis sigma(F)-dependent promoter, usfXp1. Comparison of the promoters revealed a sigma(F) consensus sequence GtTtga-N(14-18)-GGGTAT. The sigma(F)-dependent promoters may govern expression of genes encoding a transcription regulator homologous to the response regulators of bacterial two-component signal transduction systems and proteins with unknown function.
...
PMID:Identification of promoters recognized by RNA polymerase containing Mycobacterium tuberculosis stress-response sigma factor sigma(F). 1708 48

sigma factors are transcriptional regulatory proteins that bind to the RNA polymerase and dictate gene expression. The extracytoplasmic function (ECF) sigma factors govern the environment dependent regulation of transcription. ECF sigma factors have two domains sigma(2) and sigma(4) that recognize the -10 and -35 promoter elements. However, unlike the primary sigma factor sigma(A), the ECF sigma factors lack sigma(3), a region that helps in the recognition of the extended -10 element and sigma(1.1), a domain involved in the autoinhibition of sigma(A) in the absence of core RNA polymerase. Mycobacterium tuberculosis sigma(C) is an ECF sigma factor that is essential for the pathogenesis and virulence of M. tuberculosis in the mouse and guinea pig models of infection. However, unlike other ECF sigma factors, sigma(C) does not appear to have a regulatory anti-sigma factor located in the same operon. We also note that M. tuberculosis sigma(C) differs from the canonical ECF sigma factors as it has an N-terminal domain comprising of 126 amino acids that precedes the sigma(C)(2) and sigma(C)(4) domains. In an effort to understand the regulatory mechanism of this protein, the crystal structures of the sigma(C)(2) and sigma(C)(4) domains of sigma(C) were determined. These promoter recognition domains are structurally similar to the corresponding domains of sigma(A) despite the low sequence similarity. Fluorescence experiments using the intrinsic tryptophan residues of sigma(C)(2) as well as surface plasmon resonance measurements reveal that the sigma(C)(2) and sigma(C)(4) domains interact with each other. Mutational analysis suggests that the Pribnow box-binding region of sigma(C)(2) is involved in this interdomain interaction. Interaction between the promoter recognition domains in M. tuberculosis sigma(C) are thus likely to regulate the activity of this protein even in the absence of an anti-sigma factor.
...
PMID:Structural and biophysical studies on two promoter recognition domains of the extra-cytoplasmic function sigma factor sigma(C) from Mycobacterium tuberculosis. 1714 60

The bacterial RNA polymerase (RNAP) is an essential enzyme that is responsible for making RNA from a DNA template and is targeted by several antibiotics. Rifampicin was the first of such antibiotics to be described and is one of the most efficient anti-tuberculosis drugs in use. In the past five years, structural studies of bacterial RNAP and the resolution of several complexes of drugs bound to RNAP subunits have revealed molecular details of the drug-binding sites and the mechanism of drug action. This knowledge opens avenues for the development of antibiotics. Here these drugs are reviewed, together with their mechanisms and their potential interest for therapeutic applications.
...
PMID:Progress in targeting bacterial transcription. 1733 84

To understand the predominant HIV subtype and drug-resistant viruses in northwest Ethiopia, isolates from 92 antiretroviral drug-naive HIV-1-infected tuberculosis patients were analyzed. Of these patients, 90 (97.8%) were found to be infected with viral subtype C. Other isolates had subtype A (1.1%) and subtype D (1.1%). No primary mutations were associated with protease inhibitor drug resistance. One case (1.1%) had the reverse-transcriptase mutation, V75I. Two patients (2.2%) had the G190A mutation, which confers resistance to the nonnucleoside reverse transcriptase inhibitor, nevirapine. Our study demonstrates that subtype C is the major HIV-1 subtype in northwest Ethiopia. Our results also reveal that the population in the study area had been exposed to antiretrovirals and that treatment-naive patients had drug resistance mutations. Thus, our results emphasize the need for routine drug resistance monitoring in northwest Ethiopia.
...
PMID:Molecular epidemiology of HIV type 1 in treatment-naive patients in north Ethiopia. 1745 46

Bacillus subtilis and Streptomyces spp. provide tractable experimental systems for studying cellular responses to adverse environmental conditions. During conditions of extreme nutrient limitation, these prokaryotes exhibit a wide range of adaptations, including the production and secretion of antibiotics and enzymes and the formation of aerial mycelium and spores. In response to these conditions, all bacteria, but not eukaryotic microorganisms, exhibit a "stringent response," during which the unusual guanosine tetraphosphate, ppGpp, accumulates intracellularly. This is accompanied by a marked reduction in the GTP pool, due to ppGpp inhibition of IMP-dehydrogenase, and immediate repression of rRNA synthesis, due to the binding of ppGpp to RNA polymerase. This review summarizes our studies on the bacterial stringent response and its use in applied microbiology. We found that morphological differentiation results from a decrease in the pool of GTP, whereas physiological differentiation (antibiotic production) results from a more direct function of ppGpp. That is, we found that the Streptomyces GTP-binding protein Obg functions by sensing intracellular GTP levels and that certain mutations in the RNA polymerase beta-subunit circumvent dependence on ppGpp in antibiotic production. X-ray crystallographic analysis provided a structural basis for the ppGpp regulation of transcription. On the basis of these findings, we have developed the novel concept of "ribosome engineering," focusing on activation of dormant genes to elicit cellular function fully. Ribosome engineering can be applied to strain improvement, screening of novel metabolites, plant breeding, cell-free translation systems, and the treatment of tuberculosis.
...
PMID:From microbial differentiation to ribosome engineering. 1758 68


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

---