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Query: EC:6.1.1.20 (phenylalanyl-tRNA synthetase)
 358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Affinity labelling has been employed to localize the substrate-binding sites on the enzyme subunits of phenylalanyl-tRNA synthetase (L-phenylalanine:tRNAPhe-ligase, EC 6.1.1.20) of Escherichia coli MRE-600 (alpha 2 beta 2-type). N-Chlorambucilylphenylalanyl-tRNA, N-bromoacetylphenylalanyl-tRNA, tRNAPhe containing an azido group at the eighth position of the molecule (S4U), tRNAPhe containing azido groups at different points of the molecule, p-azidoanilidate of phenylalanine, adenosine 5'-trimethaphosphate and N-bromoacetyl-L-phenylalaninyladenylate were used in experiments. It has been shown that tRNA-binding sites are formed on heavy beta-subunits of the enzyme. Phenylalanyl-tRNA is also localized on beta-subunits, while the aminoacyl moiety of aminoacyl-tRNA is localized near the contact region of subunits. The phenylalanine-binding site is located on light alpha-subunits of the enzyme. Adenosine 5'-trimethaphosphate and the analogue of phenylalanyladenylate modify both types of enzyme subunits. In our opinion, the catalytic center of tRNA aminoacylation is formed in the contact region of subunits, and the aminoacyl moiety is transferred into tRNA (from the alpha- into beta-subunit in the region of their contact).
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PMID:Phenylalanyl-tRNA synthetase from E. coli MRE-600: analysis of the active site distribution on the enzyme subunits by affinity labelling. 389 48

Modification of phenylalanyl-tRNA synthetase from E. coli MRE600 by adenosine-5'-trimetaphosphate, phosphorylating analog of ATP was shown to bring about the enzyme inactivation in the reactions of tRNA aminoacylation and ATP-[32P]pyrophosphate exchange. ATP when added in the reaction mixture protects the enzyme against inactivation in both reactions and decreases the level of covalent attachment of the analog. Phenylalanine has no protective effect. tRNA exhibits slight protective effect. Adenosine-5'-trimetaphosphate modifies both types (alpha and beta) of subunits of phenylalanyl-tRNA synthetase which is of alpha 2 beta 2 structure. ATP protects both types of the enzyme subunits against the covalent attachment of the analog. Disposition of the ATP-binding centers in the contact region of the nonequivalent subunits of the enzyme was proposed. The level of covalent attachment of the analog to the enzyme exceeds the number of the enzyme active sites that may be a consequence of the other nucleotide-binding center labeling.
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PMID:[Modification of phenylalanyl-tRNA-synthetase from Escherichia coli MRE600 by adenosine-5'-trimetaphosphate]. 636 20

epsilon ATP is a substrate of phenylalanyl-tRNA synthetase and epsilon Ado is a competitive inhibitor of ATP in the reaction of tRNA aminoacylation (Ki = 1.6 mM). The association of phenylalanyl-tRNA synthetase with ATP or Ado results in synergistic binding of phenylalaninol and phenylalanine, respectively. However neither epsilon ATP nor epsilon Ado exhibit synergism. Adenosine- and ethenoadenosine-5'-trimethaphosphates are shown to be similar affinity reagents of phenylalanyl-tRNA synthetase. ATP being covalently bound to the enzyme shows essentially lower synergistic effect in comparison with free ATP. epsilon ATP-label is practically insensitive to the ligands namely ATP, Phe, phenylalaninol and is highly accessible for I- ions. The scheme of behaviour of affinity labels is assumed to be as follows: a) the formation of specific reagent-enzyme complex, b) the covalent attachment of the reagent to the enzyme, c) the covalent binding induced disruption of the specific complex formed before.
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PMID:[Adenosine- and ethenoadenosine-5'-trimetaphosphates: the effect of covalent bond formation on the state of the affinity label in the complex with phenylalanyl-tRNA-synthetase]. 639 Jan 77

Adenosine or CpCpA trinucleoside diphosphate can be aminoacylated by phenylalanyl-tRNA synthetase [L-phenylalanine:tRNAPhe ligase (AMP forming), EC 6.1.1.20] when the reaction takes place in the presence of tRNAPhe deprived of its 3' adenosine or pCpCpA terminus. This shows that, upon interaction with tRNA, a structural alteration of the enzyme's active site is achieved. This process may be a determining step in the specificity of the aminoacylation reaction.
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PMID:Conformational activation of the yeast phenylalanyl-tRNA synthetase catalytic site induced by tRNAPhe interaction: triggering of adenosine or CpCpA trinucleoside diphosphate aminoacylation upon binding of tRNAPhe lacking these residues. 701 39