Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:Q96FX7 (tRNA)
 26,753 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The functional role of the Bacillus stearothermophilus 50S ribosomal protein B-L3 (probably homologous to the Escherichia coli protein L2) was examined by chemical modification. The complex [B-L3-23S RNA] was photooxidized in the presence of rose bengal and the modified protein incorporated by reconstitution into 50S ribosomal subunits containing all other unmodified components. Particles containing photooxidized B-L3 are defective in several functional assays, including (1) poly(U)-directed poly(Phe) synthesis, (2) peptidyltransferase activity, (3) ability to associate with a [30S-poly(U)-Phe-tRNA] complex, and (4) binding of elongation factor G and GTP. The rates of loss of the partial functional activities during photooxidation of B-L3 indicate that at least two independent inactivating events are occurring, a faster one, involving oxidation of one or more histidine residues, affecting peptidyltransferase and subunit association activities and a slower one affecting EF-G binding. Therefore the protein B-L3 has one or more histidine residues which are essential for peptidyltransferase and subunit association, and another residue which is essential for EF-G-GTP binding. B-L3 may be the ribosomal peptidyltransferase protein, or a part of the active site, and may contribute functional groups to the other active sites as well.
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PMID:Evidence of the involvement of a 50S ribosomal protein in several active sites. 0 52

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate anhydride to the hydroxyl groups of homopolyribonucleotides was investigated as a chemical model of the biochemical aminoacylation of tRNA. Imidazole catalyzed transfer of phenylalanine to poly(U) increases from pH 6.5 to 7.7 and decreases above pH 7.7. At pH 7.7 approximately 10% of the phenylalanyl residues are transferred to poly(U). At pH 7.1, transfer to poly(U) was five times as great as to poly(A) and transfer to a poly(A) poly(U) double helix was negligible. At pH 7.1 approximately 45 mole percent linkages to poly(U) were monomeric phenylalanine; the remainder of the linkages were peptides of phenylalanine. The number of linkages and their lability to base and neutral hydroxylamine indicates that phenylalanine and its peptides are attached as esters to the 2' hydroxyl groups throughout poly(U) and the 2' (3') hydroxyl groups at the terminus of poly(U). These results do model the contemporary process of aminoacyl transfer to tRNA and continue to suggest that a histidine residue is in the active site of aminoacyl-tRNA-synthetases.
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PMID:Aminoacyl transfer from an adenylate anhydride to polyribonucleotides. 0 44

The photoinduced reaction of phenylalanyl-tRNA synthetase (E.C.6.1.1.20) from E.coli MRE-600 with tRNAphe containing photoreative p-N3-C6H4-NHCOCH2-group attached to 4-thiouridine sU8 (azido-tRNAphe) was investigated. The attachment of this group does not influence the dissociation constant of the complex of Phe-tRNAphe with the enzyme, however it results in sevenfold increase of Km in the enzymatic aminoacylation of tRNAphe. Under irradiation at 300 nm at pH 5.8 the covalent binding of [14C]-Phe-azido-tRNAphe to the enzyme takes place 0.3 moles of the reagent being attached per mole of the enzyme. tRNA prevents the reaction. Phenylalanine, ATP,ADP,AMP, adenosine and pyrophosphate (2.5 xx 10(-3) M) don't affect neither the stability of the tRNA-enzyme complex nor the rate of the affinity labelling. The presence of the mixture of either phenylalanine or phenylalaninol with ATP as well as phenylalaninol adenylate exhibits 50% inhibition of the photoinduced reaction. Therefore, the reaction of [14C]-Phe-azido-tRNA with the enzyme is significantly less sensitive to the presence of the ligands than the reaction of chlorambucilyl-tRNA with the reactive group attached to the acceptor end of the tRNA studied in 1. It has been concluded that the kinetics of the affinity labelling does permit to discriminate the influence of the low molecular weight ligands of the enzyme on the different sites of the tRNA enzyme interaction.
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PMID:Affinity labelling of phenylalanyl-tRNA synthetase from E. coli MRE-600 by E. coli tRNAphe containing photoreactive group. 0 72

After T4 bacteriophage infects Escherichia coli, a peptide tau, produced under the control of a phage gene, binds to the host valyl transfer ribonucleic acid synthetase (EC 6.1.1.9) and thereby changes several of its physicochemical properties. The interaction of tau with the host enzyme was investigated in vitro after extensively purifying the factor from T4-infected E. coli using a rapid purification procedure. The tau preparation migrated as a single, protein-staining band with a molecular weight of 11,000 during sodium dodecyl sulfate-gel electrophoresis. The purified peptide completely converted partially purified valyl-tRNA synthetase from uninfected E. coli into the form present in cell-free extracts prepared from virus-infected bacteria. The enzyme modified in vitro also exhibited the enhanced affinity for tRNA characteristic of the viral form of valyl-tRNA synthetase. The addition of bulk tRNA from E. coli B, tRNAVal, or tRNA1Val to enzyme modified in vitro increased its sedimentation rate to that of enzyme prepared from phage-infected cells. Amino acid analysis of the purified tau peptide revealed a relatively high concentration of the amino acids lysine and alanine, and a lack of detectable proline, tyrosine, phenylalanine, and methionine.
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PMID:Purification and properties of a T4 bacteriophage factor that modifies valyl-tRNA synthetase of Escherichia coli. 1 75

Effect of tryptophan force-feeding to well-fed adrenalectomized rats on the ability of liver cell sap and initiation factors to support protein synthesis in vitro was investigated. 5 h after tryptophan force-feeding, the capacity of liver cell sap, pH 5 enzyme and pH 5 supernatant to support protein synthesis was greatly increased. The capacity of cell sap to support charging of tRNA with either (14C)-leucine or (14C)-phenylalanine was increased following a dose of tryptophan. Initiation factors prepared from tryptophan-fed adrenalectomized rats stimulated polyuridylic-acid-directed polyphenylalanine synthesis to a greater extent than those from livers of water-fed adrenalectomized controls.
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PMID:Bilateral adrenalectomy: factors affecting hepatic protein synthesis following a single tube-feeding of tryptophan. 2 22

The ribosomal protein S1 was modified by reductive methylation of some of its lysyl ammonium groups (S1). With 6 out of 30 groups methylated the protein lost its capacity to form stable complexes with polyuridylate. Addition of excess polyuridylate inhibited the methylation of the lysyl groups. In equilibrium dialysis experiments it was shown that the binding constant between S1 and U15 was lowered 10-fold as compared to the native protein. The pH-dependence of the complex formation between S1 and U15 confirms a participation of the lysyl residues. When S1 depleted 30-S ribosomes were reconstituted with methylated S1 these ribosomes were inactive in the poly(U) stimulated Phe-tRNA binding. The data are discussed with respect to a grid-like interaction between the lysyl groups of the protein and the phosphodiester bonds of the polynucleotide as a molecular basis of protein nucleic acid interaction.
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PMID:Inactivation of the ribosomal protein S1 in polyuridylate binding by reductive methylation of the lysyl-ammonium groups. 3 5

Spermine and spermidine added to a Saccharomyces cerevisiae cell-free protein synthesizing system increased phenylalanine polymerization reaction several-fold at suboptimal concentration of Mg2+ and approximately two-fold at optimal amounts of Mg2+. The addition of polyamines greatly stimulated the enzymatic and nonenzymatic binding of phenylalanyl-tRNA and N-acetylphenylalanyl-tRNA to ribosomes. The binding of the acetylated derivative was higher than phenylalanyl-tRNA, however, as it was shown the former was bound exclusively to the A site of the ribosome. Contrary to the binding process, the puromycin reaction was not stimulated by spermine added at a concentration which enhanced the polyphenylalanine synthesis. These results indicate that polyamines have not only a sparing effect on the Mg2+ requirement for yeast protein synthesis in vitro and suggest that one of the possible sites of polyamines action might be the binding of aminoacyl-tRNA to ribosomes.
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PMID:Effect of polaymines on yeast cell-free protein synthesizing system. I. Influence of spermine and spermidine on aminoacyl-tRNA transfer reaction. 6 94

As previously reported (G. H. Jones, 1975), transfer ribonucleic acids (tRNA's) and ribosomes from actinomycin-producing cultures of Streptomyces antibioticus show a decreased ability to function in aminoacylation and translation as compared with the corresponding components from younger cells. Further, specific changes in the isoacceptor patterns are revealed when tRNA's from actinomycin-producing cells are compared with those of younger cells by reverse- phase column chromatography. A specific glycyl-tRNA species is eliminated from the reverse-phase profile of tRNA's from actinomycin-producing S. antibioticus cells as compared with younger cells. Changes in isoacceptor patterns were also observed for the amino acids methionine, valine, phenylalanine, and leucine. Actinomycin synthesis was inhibited by growing S. antibioticus cells in the presence of alpha-methyl-DL-tryptophan. Inhibition of actinomycin synthesis reversed the changes in tRNA observed in normally grown control cultures, although it had no demonstrable effect on the growth of the cells. Thus, tRNA from 48-h-old, alpha-methyl-tryptophan-grown cells had amino acid acceptor activity that was equal to or greater than that of tRNA from 12-h-old, normally grown cells. Similarly, the reverse-phase chromatographic pattern for glycyl-tRNA's from 48-h-old, alpha-methyl-tryptophan-grown cells was identical to that of the glycyl-tRNA's from 12-h-old, normally grown cells. In contrast, the ability of ribosomes from 48-h-old, alpha-methyl-tryptophan-grown cells to function in polypeptide synthesis in vitro was essentially identical to that of 48-h-old, normally grown cells. Ribosomes from 12-h-old, normally grown cells were severalfold more active in in vitro polypeptide synthesis.
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PMID:Relationship between changes in the translational apparatus and actinomycin production in Streptomyces antibioticus. 6 58

The introduction of antigenic determining 2,4-dinitrophenyl residues into the rare ribonucleosides 4-thiouridine (1a), and N3-(3-L-amino-3-carboxypropyl) uridine (2) as well as into tRNA-Phe from E. coli has been investigated. Alkylation of 1a with omega-bromo-2,4-dinitroacetophenone (3b) gives S-(2,4-dinitrophenacyl)-4-thiouridine (5A). Applying the reaction to the 5'-monophosphate of 1a, 5b is formed, but this product decomposes at pH 7. However, acylation of 2 with 2,4-dinitrobenzoic acid N-hydroxysuccinimide ester (4b) leads to N3-[3-carboxy-3-L-(2,4-dinitrobenzamido)propyl]uridine (6) which is stable in aqueous solution. The latter reaction was used for the introduction of an antigenic determining 2,4-dinitrophenyl residue into tRNA-Phe from E. coli. The modified tRNA-Phe was isolated and by degradation of the molecule with RNase T2 and alkaline phosphatase the nucleoside derivative 6 was obtained and found to be identical with the synthetic product.
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PMID:Introduction of antigenic determining 2,4-dinitrophenyl residues into 4-thiouridine, N3-(3-L-amino-3-carboxypropyl) uridine and tRNA-Phe from E. coli. 6 63

The accessibility of each 30S subunit protein to their cognate antibodies (IgG or Fabs) having been previously well established, the effect of their in situ specific neutralization by monovalent IgG fragments (FabI) are reported for five reactions: 1) T4 and R17 RNA directed protein synthesis: 2) polyphenylalanine synthesis: 3) enzymatic Phe-tRNA binding in the presence of 30S + 50W subunits: 4) fMet-tRNAf binding to the 30S subunit in the presence of initiation factors IF1, IF2, IF3; 5) coupling with lambda plac DNA transcription of the initial translation step (i.e., interaction of IF3 activated 30S subunits with nascent mRNA, in the absence of tRNA). According to evident similarities in their inhibition pattern concerning the five reactions tested, 30S subunit proteins can be classified in five categories which are discussed in terms of functional topography.
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PMID:Function of individual E. coli 30 S ribosomal proteins as determined by in situ immunospecific neutralization: a tentative classification. 9 93


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