scholarly journals Properties and substrate specificities of the phenylalanyl-transfer-ribonucleic acid synthetases of Aesculus species

1970 ◽  
Vol 119 (4) ◽  
pp. 677-690 ◽  
Author(s):  
J. W. Anderson ◽  
L. Fowden
Keyword(s):  
Amino Acid ◽  
Maximum Velocity ◽  
Dienoic Acid ◽  
Trna Synthetase ◽  
Enoic Acid ◽  
Synthetase Activity ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Phenylbutyric Acid ◽  
Exchange Activity

1. Phenylalanyl-tRNA synthetases have been partially purified from cotyledons of seeds of Aesculus californica, which contains 2-amino-4-methylhex-4-enoic acid, and from four other species of Aesculus that do not contain this amino acid. The A. californica preparation was free from other aminoacyl-tRNA synthetases, and the contaminating synthetase activity in preparations from A. hippocastanum was decreased to acceptable limits by conducting assays of pyrophosphate exchange activity in 0.5m-potassium chloride. 2. The phenylalanyl-tRNA synthetase from each species activated 2-amino-4-methylhex-4-enoic acid with Km 30–40 times that for phenylalanine. The maximum velocity for 2-amino-4-methylhex-4-enoic acid was only 30% of that for phenylalanine with the A. californica enzyme, but the maximum velocities for the two substrates were identical for the other four species. 3. 2-Amino-4-methylhex-4-enoic acid was not found in the protein of A. californica, so discrimination against this amino acid probably occurs in the step of transfer to tRNA, though subcellular localization, or subsequent steps of protein synthesis could be involved. 4. Crotylglycine, methallylglycine, ethallylglycine, 2-aminohex-4,5-dienoic acid, 2-amino-5-methylhex-4-enoic acid, 2-amino-4-methylhex-4-enoic acid, β-(thien-2-yl)alanine, β-(pyrazol-1-yl)alanine, phenylserine and m-fluorophenylalanine were substrates for pyrophosphate exchange catalysed by the phenylalanyl-tRNA synthetases of A. californica or A. hippocastanum. Allylglycine, phenylglycine and 2-amino-4-phenylbutyric acid were inactive.

scholarly journals A novel pathway for the conversion of homocysteine to methionine in eukaryotes

1997 ◽  
Vol 328 (1) ◽  
pp. 165-170 ◽  
Author(s):  
M. Celia ANTONIO ◽  
C. Marta NUNES ◽  
Helga REFSUM ◽  
K. Abraham ABRAHAM
Keyword(s):  
Amino Acid ◽  
Crude Extract ◽  
Trna Synthetase ◽  
Synthetase Activity ◽  
Enzyme Complex ◽  
Homocysteine Thiolactone ◽  
Initiator Trna ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Reticulocyte Lysates

Activation of amino acid homocysteine was compared with that of methionine in rabbit crude liver extracts and purified multi-enzyme complex of aminoacyl-tRNA synthetases. Activation was studied by measuring the incorporation of radioactive amino acid into unlabelled trichloroacetic-acid insoluble materials in the absence of protein synthesis. Homocysteine synthetase activity was found in the crude extract and in the purified multi-enzyme complex of aminoacyl-tRNA synthetases. On a molar basis, the activation of methionine by the crude extract was five times higher than the activation of homocysteine. There was a partial loss of Hcy-tRNA synthetase activity in the purified multi-enzyme complex. Preliminary reconstitution experiments indicated a requirement for an additional factor for Hcy-tRNA synthetase activity. TLC of the amino acid released from tRNA charged with [14C]homocysteine, revealed radioactivity in homocysteine, methionine and homocysteine thiolactone, indicating a conversion of tRNA-attached homocysteine to methionine. Total tRNA was separated on a benzoylated cellulose column into a fraction enriched in initiator tRNA and a methionine-accepting, but initiator tRNA-deficient, fraction. Homocysteine-accepting activity was present only in the initiator tRNA-enriched fraction. Based on the above data we propose that homocysteine activation in reticulocyte lysates, reported previously, also occurs in liver. Activated homocysteine is attached to initiator tRNA and then converted to methionine by a methylating enzyme. In the absence of methylation, tRNA-attached homocysteine is hydrolysed to produce homocysteine thiolactone.

scholarly journals Bacterial Aspartyl-tRNA Synthetase Has Glutamyl-tRNA Synthetase Activity

Genes ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 262 ◽  
Author(s):  
Udumbara M. Rathnayake ◽  
Tamara L. Hendrickson
Keyword(s):  
Amino Acid ◽  
Genetic Code ◽  
Trna Synthetase ◽  
Synthetase Activity ◽  
Messenger Rnas ◽  
Indirect Pathway ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases

The aminoacyl-tRNA synthetases (aaRSs) are well established as the translators of the genetic code, because their products, the aminoacyl-tRNAs, read codons to translate messenger RNAs into proteins. Consequently, deleterious errors by the aaRSs can be transferred into the proteome via misacylated tRNAs. Nevertheless, many microorganisms use an indirect pathway to produce Asn-tRNAAsn via Asp-tRNAAsn. This intermediate is produced by a non-discriminating aspartyl-tRNA synthetase (ND-AspRS) that has retained its ability to also generate Asp-tRNAAsp. Here we report the discovery that ND-AspRS and its discriminating counterpart, AspRS, are also capable of specifically producing Glu-tRNAGlu, without producing misacylated tRNAs like Glu-tRNAAsn, Glu-tRNAAsp, or Asp-tRNAGlu, thus maintaining the fidelity of the genetic code. Consequently, bacterial AspRSs have glutamyl-tRNA synthetase-like activity that does not contaminate the proteome via amino acid misincorporation.

scholarly journals Polyribosomal and particulate distribution of lysyl- and phenylalanyl-transfer ribonucleic acid synthetases

1974 ◽  
Vol 143 (1) ◽  
pp. 191-195 ◽  
Author(s):  
Gale Moline ◽  
Arnold Hampel ◽  
M. Duane Enger
Keyword(s):  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Trna Synthetase ◽  
Differential Sensitivity ◽  
Synthetase Activity ◽  
Ribosomal Subunits ◽  
Ovary Cells ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Particulate Distribution

1. Only two aminoacyl-tRNA synthetases from Chinese hamster ovary cells are found associated with ribosomes and polyribosomes. 2. Phenylalanyl-tRNA synthetase activity is found with the 60S subunit, 80S monoribosome and individual polyribosomes. An additional 15S form of the enzyme is also seen. 3. Lysyl-tRNA synthetase activity is found in a form of about 20S and associated with ribosomal subunits and polyribosomes. The ribosomal subunits having lysyl-tRNA synthetase activity are about 6S larger than the bulk of the ribosomal subunits. 4. The lysyl- and phenylalanyl-tRNA synthetases found in different complexes have differential sensitivity to EDTA and centrifugation properties.

scholarly journals Effects of liver regeneration on tRNA contents and aminoacyl-tRNA synthetase activities and sedimentation patterns

1986 ◽  
Vol 236 (1) ◽  
pp. 163-169 ◽  
Author(s):  
U Del Monte ◽  
S Capaccioli ◽  
G Neri Cini ◽  
R Perego ◽  
R Caldini ◽  
...  
Keyword(s):  
Protein Degradation ◽  
Cultured Cells ◽  
Trna Synthetase ◽  
Synthetase Activity ◽  
Regenerating Liver ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Acceptor Capacity ◽  
Increased Activity

The tRNA content and aminoacyl-tRNA synthetases of regenerating liver in the phase of rapid growth were compared with those of livers from both intact and sham-operated rats. At 48 h after hepatectomy, the amount of active tRNA (called ‘total acceptor capacity’) is significantly higher in regenerating liver than in control livers, owing to a general, possibly not uniform, increase in the various tRNA families, which suggests that it may contribute to the increased protein synthesis and to decreased protein degradation as well. The activities of most, but not of all, aminoacyl-tRNA synthetases in cell sap of regenerating liver tend to be greater than normal. Increased activity of histidyl-tRNA synthetase fits in with the possibility that the mechanisms that control the rate of protein degradation through aminoacylation of tRNAHis in cultured cells [Scornik (1983) J. Biol. Chem. 258, 882-886] also operate in the liver and play a role in regeneration. Sedimentation analysis of cell sap in sucrose density gradients shows a shift of prolyl-tRNA synthetase activity toward the high-Mr form in regenerating liver. This change might be related to the positive protein balance and to growth in vivo, since it is also observed in the anaplastic Yoshida ascites hepatoma AH 130.

A Genetic Study of Erythrocyte Arginine-tRNA Synthetase Activity in Man

1977 ◽  
Vol 26 (1) ◽  
pp. 21-27 ◽  
Author(s):  
Sylvia A. McCune ◽  
P. L. Yu ◽  
Walter E. Nance
Keyword(s):  
Enzyme Activity ◽  
Trna Synthetase ◽  
Synthetase Activity ◽  
Trna Synthetases ◽  
Automated Assay ◽  
Aminoacyl Trna Synthetases ◽  
Assay Procedure ◽  
Normal Human ◽  
Genetically Determined ◽  
Mz Twins

To search for evidence of genetic variation among the aminoacyl-tRNA synthetases, a semi-automated assay procedure employing a Technicon Auto Analyzer was used to measure erythrocyte arginine-tRNA synthetase activity in samples obtained from normal human twins of various ages. Variation in enzyme activity within the older DZ twins was five times that of the MZ twins suggesting the existence of genetically determined variation in enzyme activity. Higher enzyme activity was observed in newborn DZ unlike-sexed twins than in like-sexed twins of either zygosity. Possible explanations for this observation are discussed.

Structure of nondiscriminating glutamyl-tRNA synthetase fromThermotoga maritima

2010 ◽  
Vol 66 (7) ◽  
pp. 813-820 ◽  
Author(s):  
Takuhiro Ito ◽  
Noriko Kiyasu ◽  
Risa Matsunaga ◽  
Seizo Takahashi ◽  
Shigeyuki Yokoyama
Keyword(s):  
Crystal Structure ◽  
Amino Acid ◽  
Thermotoga Maritima ◽  
Trna Synthetase ◽  
Characteristic Structure ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Rossmann Fold

Aminoacyl-tRNA synthetases produce aminoacyl-tRNAs from the substrate tRNA and its cognate amino acid with the aid of ATP. Two types of glutamyl-tRNA synthetase (GluRS) have been discovered: discriminating GluRS (D-GluRS) and nondiscriminating GluRS (ND-GluRS). D-GluRS glutamylates tRNAGluonly, while ND-GluRS glutamylates both tRNAGluand tRNAGln. ND-GluRS produces the intermediate Glu-tRNAGln, which is converted to Gln-tRNAGlnby Glu-tRNAGlnamidotransferase. Two GluRS homologues fromThermotoga maritima, TM1875 and TM1351, have been biochemically characterized and it has been clarified that only TM1875 functions as an ND-GluRS. Furthermore, the crystal structure of theT. maritimaND-GluRS, TM1875, was determined in complex with a Glu-AMP analogue at 2.0 Å resolution. TheT. maritimaND-GluRS contains a characteristic structure in the connective-peptide domain, which is inserted into the catalytic Rossmann-fold domain. The glutamylation ability of tRNAGlnby ND-GluRS was measured in the presence of the bacterial Glu-tRNAGlnamidotransferase GatCAB. Interestingly, the glutamylation efficiency was not affected even in the presence of excess GatCAB. Therefore, GluRS avoids competition with GatCAB and glutamylates tRNAGln.

scholarly journals Aminoacyl tRNA Synthetases as Malarial Drug Targets: A Comparative Bioinformatics Study

2018 ◽  
Author(s):  
Dorothy Wavinya Nyamai ◽  
Özlem Tastan Bishop
Keyword(s):  
Amino Acid ◽  
Drug Targets ◽  
Motif Discovery ◽  
Protein Translation ◽  
Trna Synthetase ◽  
Potential Drug ◽  
Multiple Sequence ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
Potential Drug Targets

AbstractTreatment of parasitic diseases has been challenging due to the development of drug resistance by parasites, and thus there is need to identify new class of drugs and drug targets. Protein translation is important for survival of plasmodium and the pathway is present in all the life cycle stages of the plasmodium parasite. Aminoacyl tRNA synthetases are primary enzymes in protein translation as they catalyse the first reaction where an amino acid is added to the cognate tRNA. Currently, there is limited research on comparative studies of aminoacyl tRNA synthetases as potential drug targets. The aim of this study is to understand differences between plasmodium and human aminoacyl tRNA synthetases through bioinformatics analysis. Plasmodium falciparum, P. fragile, P. vivax, P. ovale, P. knowlesi, P. bergei, P. malariae and human aminoacyl tRNA synthetase sequences were retrieved from UniProt database and grouped into 20 families based on amino acid specificity. Despite functional and structural conservation, multiple sequence analysis, motif discovery, pairwise sequence identity calculations and molecular phylogenetic analysis showed striking differences between parasite and human proteins. Prediction of alternate binding sites revealed potential druggable sites in PfArgRS, PfMetRS and PfProRS at regions that were weakly conserved when compared to the human homologues. These differences provide a basis for further exploration of plasmodium aminoacyl tRNA synthetases as potential drug targets.

scholarly journals Oxidation of cellular amino acid pools leads to cytotoxic mistranslation of the genetic code

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Tammy J Bullwinkle ◽  
Noah M Reynolds ◽  
Medha Raina ◽  
Adil Moghal ◽  
Eleftheria Matsa ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Genetic Code ◽  
Trna Synthetase ◽  
Control Mechanisms ◽  
Cellular Toxicity ◽  
Trna Synthetases ◽  
Aminoacyl Trna Synthetases ◽  
The Cost

Aminoacyl-tRNA synthetases use a variety of mechanisms to ensure fidelity of the genetic code and ultimately select the correct amino acids to be used in protein synthesis. The physiological necessity of these quality control mechanisms in different environments remains unclear, as the cost vs benefit of accurate protein synthesis is difficult to predict. We show that in Escherichia coli, a non-coded amino acid produced through oxidative damage is a significant threat to the accuracy of protein synthesis and must be cleared by phenylalanine-tRNA synthetase in order to prevent cellular toxicity caused by mis-synthesized proteins. These findings demonstrate how stress can lead to the accumulation of non-canonical amino acids that must be excluded from the proteome in order to maintain cellular viability.

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