Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A study of the recognition of tRNA(Cys) by Escherichia coli cysteinyl-tRNA synthetase using in vivo and in vitro methods was performed. All three anticodon nucleotides, the discriminator nucleotide (73), and some elements within the tertiary domain (the D stem/loop, the T psi C stem/loop, and the variable loop) are important for recognition; the anticodon stem and acceptor stem appear to contain no essential elements. A T7 RNA polymerase transcript corresponding to tRNA(Cys) is only a 5.5-fold worse substrate than native tRNA(Cys) (in terms of the specificity constant, kcat/Km), mainly due to an increase in the value of Km for the transcript. The greatest loss of specificity caused by mutation of a single nucleotide occurs when the discriminator U73 is changed; kcat/Km declines 3-4 orders of magnitude depending on the substitution. Mutations in the wobble nucleotide of the anticodon also cause reductions in the specificity constant of 3 orders of magnitude, while mutations in the other anticodon nucleotides caused lesser effects. Interestingly, a C35A mutation (with the phenylalanine anticodon GAA) had no effect on aminoacylation by the cysteinyl-tRNA synthetase. Several amber suppressor tRNAs were constructed whose in vivo identity did not correlate with their in vitro specificity, indicating the need for both types of experiments to understand the factors which maintain tRNA specificity.
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PMID:Recognition of tRNA(Cys) by Escherichia coli cysteinyl-tRNA synthetase. 833 41

Mycoplasma hyopneumoniae causes swine pneumonia and contributes significantly to the porcine respiratory disease complex. The mechanisms of pathogenesis are difficult to address, since there is a lack of genetic tools, but microarrays are available and can be used to study transcriptional changes that occur during disease as a way to identify important virulence-related genes. Mycoplasmas were collected from bronchial alveolar lavage samples and compared to broth-grown cells using microarrays. Bronchial alveolar lavage was performed on pigs 28 days postinfection, and mycoplasmas were isolated by differential centrifugation. Mycoplasma RNA-enriched preparations were then obtained from total RNA by subtracting eucaryotic ribosomal and messenger RNAs. Labeled cDNAs were generated with mycoplasma open reading frame-specific primers. Nine biological replicates were analyzed. During lung infection, our analysis indicated that 79 M. hyopneumoniae genes were differentially expressed (P < 0.01), at a false-discovery rate of <2.7%. Of the down-regulated genes, 28 of 46 (61%) lacked an assigned function, in comparison to 21 of 33 (63%) of up-regulated genes. Four down-regulated genes and two up-regulated genes encoded putative lipoproteins. secA (mhp295) (P = 0.003) and two glycerol transport permease genes (potA [mhp380; P = 0.006] and ugpA [mhp381; P = 0.003]) were up-regulated in vivo. Elongation factor EF-G (fusA [mhp083]) (P = 0.002), RNA polymerase beta chain (rpoC [mhp635]) (P = 0.003), adenylate kinase (adk [mhp208]) (P = 0.001), prolyl aminoacyl tRNA synthetase (proS [mhp397]) (P = 0.009), and cysteinyl-tRNA synthetase (cysS [mhp661]) (P < 0.001) were down-regulated in vivo.
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PMID:Transcriptome changes in Mycoplasma hyopneumoniae during infection. 1807 Aug 98