Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report the development of a bisubstrate reagent that, similar to tyrosyl t-RNA synthetase (TyrTS), provides a surface for ATP and l-Tyr to render a pseudo-intramolecular reaction forming 5'-tyrosyl adenylate (tyrAd). The presence of the reagent in solution with TyrTS marred the enzymatic reaction and, noticeably, tyrAd formed under the catalytic mode of the biomodel reagent was not picked up by TyrTS and hence was not transferred to tRNA. A potential application of this reagent, which doesn't allow the formation of tyrosyl tRNA, may lie in an emerging therapeutic targeting the translation machinery of cells without inhibiting the normal workings of enzymes.
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PMID:A bisubstrate reagent orchestrating adenosine triphosphate and l-tyrosine and making tyrosyl adenylate: partial mimicking of tyrosyl-tRNA synthetase. 3051 4

Coronavirus nonstructural protein 8 (nsp8) has been suggested to have diverse activities, including noncanonical template-dependent polymerase activities. Here, we characterized a recombinant form of the human coronavirus 229E (HCoV-229E) nsp8 and found that the protein has metal ion-dependent RNA 3'-terminal adenylyltransferase (TATase) activity, while other nucleotides were not (or very inefficiently) transferred to the 3' ends of single-stranded and (fully) double-stranded acceptor RNAs. Using partially double-stranded RNAs, very efficient TATase activity was observed if the opposite (template) strand contained a short 5' oligo(U) sequence, while very little (if any) activity was detected for substrates with other homopolymeric or heteropolymeric sequences in the 5' overhang. The oligo(U)-assisted/templated TATase activity on partial-duplex RNAs was confirmed for two other coronavirus nsp8 proteins, suggesting that the activity is conserved among coronaviruses. Replacement of a conserved Lys residue with Ala abolished the in vitro RNA-binding and TATase activities of nsp8 and caused a nonviable phenotype when the corresponding mutation was introduced into the HCoV-229E genome, confirming that these activities are mediated by nsp8 and critical for viral replication. In additional experiments, we obtained evidence that nsp8 has a pronounced specificity for adenylate and is unable to incorporate guanylate into RNA products, which strongly argues against the previously proposed template-dependent RNA polymerase activity of this protein. Given the presence of an oligo(U) stretch at the 5' end of coronavirus minus-strand RNAs, it is tempting to speculate (but remains to be confirmed) that the nsp8-mediated TATase activity is involved in the 3' polyadenylation of viral plus-strand RNAs.IMPORTANCE Previously, coronavirus nsp8 proteins were suggested to have template-dependent RNA polymerase activities resembling those of RNA primases or even canonical RNA-dependent RNA polymerases, while more recent studies have suggested an essential cofactor function of nsp8 (plus nsp7) for nsp12-mediated RNA-dependent RNA polymerase activity. In an effort to reconcile conflicting data from earlier studies, the study revisits coronavirus nsp8-associated activities using additional controls and proteins. The data obtained for three coronavirus nsp8 proteins provide evidence that the proteins share metal ion-dependent RNA 3' polyadenylation activities that are greatly stimulated by a short oligo(U) stretch in the template strand. In contrast, nsp8 was found to be unable to select and incorporate appropriate (matching) nucleotides to produce cRNA products from heteropolymeric and other homooligomeric templates. While confirming the critical role of nsp8 in coronavirus replication, the study amends the list of activities mediated by coronavirus nsp8 proteins in the absence of other proteins.
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PMID:Identification and Characterization of a Human Coronavirus 229E Nonstructural Protein 8-Associated RNA 3'-Terminal Adenylyltransferase Activity. 3091 70


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