Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The appearance of drug resistant strains of herpes simplex virus type 1 (HSV-1) against 9-beta-D-arabinofuranosyladenine (araA), in comparison with 5-iodo-2'-deoxyuridine (IUdR) and 9-(2-hydroxyethoxymethyl)guanine (acycloguanosine, ACG), has been investigated in green monkey kidney cell cultures (Vero) and human embryo lung cell cultures (HEL). Growth curves of HSV-1 in Vero cells and HEL cells in the presence or absence of 20 micrograms/ml of araA showed that not only the viruses produced by these cells in the presence of araA but also the viruses produced in the absence of araA were resistant to the same concentration of araA. However, both viruses were unable to grow in the presence of a combination of 20 micrograms/ml of araA and 3 micrograms/ml of erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) which is an inhibitor of adenosine deaminase. On the other hand, the viruses produced only in the presence of IUdR or ACG were resistant to each drug. All virus clones obtained from five serial clonings in the presence of araA alone or araA and EHNA in combination were not resistant to araA. These results show that the strain of HSV-1 resistant to araA is an apparently resistant strain, and a truly resistant strain to araA may not be established as easily as the truly resistant strains to IUdR and ACG.
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PMID:Study on the apparent resistant strains of herpes simplex virus type 1 against 9-beta-D-arabinofuranosyladenine. 285 80

We have investigated the specificity of the tRNA modifying enzyme that transforms the adenosine at position 34 (wobble position) into inosine in the anticodon of several tRNAs. For this purpose, we have constructed sixteen recombinants of yeast tRNAAsp harboring an AXY anticodon (where X or Y was one of the four nucleotides A, G, C or U). This was done by enzymatic manipulations in vitro of the yeast tRNAAsp, involving specific hydrolysis with S1-nuclease and RNAase A, phosphorylation with T4-polynucleotide kinase and ligation with T4-RNA ligase: it allowed us to replace the normal anticodon GUC by trinucleotides AXY and to introduce simultaneously a 32P-labelled phosphate group between the uridine at position 33 and the newly inserted adenosine at position 34. Each of these 32P-labelled AXY "anticodon-substituted" yeast tRNAAsp were microinjected into the cytoplasm of Xenopus laevis oocytes and assayed for their capacity to act as substrates for the A34 to I34 transforming enzyme. Our results indicate that: 1/ A34 in yeast tRNAAsp harboring the arginine anticodon ACG or an AXY anticodon with a purine at position 35 but with A, G or C but not U at position 36 were efficiently modified into I34; 2/ all yeast tRNAAsp harboring an AXY anticodon with a pyrimidine at position 35 (except ACG) or uridine at position 36 were not modified at all. This demonstrates a strong dependence on the anticodon sequence for the A34 to I34 transformation in yeast tRNAAsp by the putative cytoplasmic adenosine deaminase of Xenopus laevis oocytes.
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PMID:Enzymatic conversion of adenosine to inosine in the wobble position of yeast tRNAAsp: the dependence on the anticodon sequence. 636 51

Plastids (chloroplasts) of higher plants exhibit two types of conversional RNA editing: cytidine-to-uridine editing in mRNAs and adenosine-to-inosine editing in at least one plastid genome-encoded tRNA, the tRNA-Arg(ACG). The enzymes catalyzing RNA editing reactions in plastids are unknown. Here we report the identification of the A-to-I tRNA editing enzyme from chloroplasts of the model plant Arabidopsis thaliana. The protein (AtTadA) has an unusual structure in that it harbors a large N-terminal domain of >1000 amino acids, which is not required for catalytic activity. The C-terminal region of the protein displays sequence similarity to tadA, the tRNA adenosine deaminase from Escherichia coli. We show that AtTadA is imported into chloroplasts in vivo and demonstrate that the in vitro translated protein triggers A-to-I editing in the anticodon of the plastid tRNA-Arg(ACG). Suppression of AtTadA gene expression in transgenic Arabidopsis plants by RNAi results in reduced A-to-I editing in the chloroplast tRNA-Arg(ACG). The RNAi lines display a mild growth phenotype, presumably due to reduced chloroplast translational efficiency upon limited availability of edited tRNA-Arg(ACG).
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PMID:Identification of the chloroplast adenosine-to-inosine tRNA editing enzyme. 1946 Aug 69

RNA editing changes the coding/decoding information relayed by transcripts via nucleotide insertion, deletion, or conversion. Editing of tRNA anticodons by deamination of adenine to inosine is used both by eukaryotes and prokaryotes to expand the decoding capacity of individual tRNAs. This limits the number of tRNA species required for codon-anticodon recognition. We have identified the Arabidopsis thaliana gene that codes for tRNA adenosine deaminase arginine (TADA), a chloroplast tRNA editing protein specifically required for deamination of chloroplast (cp)-tRNAArg(ACG) to cp-tRNAArg(ICG). Land plant TADAs have a C-terminal domain similar in sequence and predicted structure to prokaryotic tRNA deaminases and also have very long N-terminal extensions of unknown origin and function. Biochemical and mutant complementation studies showed that the C-terminal domain is sufficient for cognate tRNA deamination both in vitro and in planta. Disruption of TADA has profound effects on chloroplast translation efficiency, leading to reduced yields of chloroplast-encoded proteins and impaired photosynthetic function. By contrast, chloroplast transcripts accumulate to levels significantly above those of wild-type plants. Nevertheless, absence of cp-tRNAArg(ICG) is compatible with plant survival, implying that two out of three CGN codon recognition occurs in chloroplasts, though this mechanism is less efficient than wobble pairing.
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PMID:Arabidopsis tRNA adenosine deaminase arginine edits the wobble nucleotide of chloroplast tRNAArg(ACG) and is essential for efficient chloroplast translation. 1960 23