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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A comparative study of the position specificity of tRNA-methylases from normal and tumour tissues was performed on yeast tRNA1Val as the substrates using partially purified enzyme preparations from rat kidney and carcinoma RA. As in the case of rat liver and Novikoff hepatoma, two methylated compounds are formed in yeast tRNA1Val under the action of rat kidney and carcinoma enzyme preparations: m5C is formed in the sequence C49--C52 located in the extra loop and A59 in the Tpsi-loop is is converted into m1A. The activity of m5C-methylase [S-Ado-Met-tRNA-(cytosine-5)methyltransferase] (E. C. 2.1.1.29) is approximately equal in both tissues, whereas the activity of m1A-methylase [S-Ado-Met-tRNA-(adenine-1)methyltransferase] (E. C. 2.1.1.36) in carcinoma is twice as high as in the kidney. The two enzymes do not differ in their position specificity.
Mol Biol (Mosk)
PMID:[Comparative study of the tRNA-methylases of normal and tumor tissues. II. Positional specificity of renal and carcinoma RA methylases]. 61 46

Six UV induced cycloheximide-sensitive revertants were isolated from the cyh1-C7 strain of Schizosaccharomyces pombe which is resistant to cycloheximide. In all cases reversion to sensitivity was due to a forward mutation in a second suppressor gene. Genetical analysis showed that at least two genes, designated scr1 and scr2 (scr=suppression of cycloheximide resistance) were involved. Both scr1 and scr2 suppressed the resistance of six independently isolated alleles at the cyh1 locus. They had no effect on two known nonsense mutations in the ade7 locus. The cyh1-C7 strain has an altered 60S ribosomal protein which can be detected by two-dimensional polyacrylamide gel electrophoresis. In two suppressed strains, cyh1-C7 scr1 and cyh1-C7 scr2, the original altered protein was present. However no further ribosomal protein differences were observed which could be correlated with the presence of the scr genes. Both scr mutations conferred cold sensitivity on the organism indicating that they were of the missense type. Hence it seems certain that scr1 and scr2 are not mutations in tRNA genes leading to either nonsense or missense suppression. There is however no direct evidence that they code for ribosomal proteins and exert their effect on cyh1-C7 at the ribosomal level.
Mol Gen Genet 1978 Jun 14
PMID:Genetical studies on revertants to sensitivity from a cycloheximide resistant strain of Schizosaccharomyces pombe. 67 2

A new type of sorbents for affinity chromatography is suggested and used to purify tRNA methylases. tRNA was immobilized on aminooxybutylcellulose via the oxidized 3'-end. In order to bind other enzymes specific for nucleic acids in general, e. g. nucleases, and to achieve a higher degree of purification the crude enzyme preparation was treated with rRNA immobilized on aminooxybutycellulose. The sequential application of two sorbents mentioned allows to get an approximately two hundred fold purification of total tRNA methylases. In a separate experiment the possibility of individual tRNA methylase fractionation by means of elution with a NACl gradient was shown; the degree of purification for some methylases was more than a thousand fold.
Mol Biol (Mosk)
PMID:[Amino oxyadsorbents. New type of adsorbents for affinity chromatography: purification of tRNA-methylases from rat nephron on aminooxybutylcellulose with immobilized tRNA]. 73 96

Low molecular weight (LMW) RNAs from early fish embryos were characterized by investigating their migration in polyacrylamide gels, solubility in 1.5 M NaCl, in vivo methylation by the methionine methyl group, metabolic stability, and effects of low doses of alpha-amanitin on their syntheses. At blastula stage, the mature tRNA and 4.3--4.8 S metabolically unstable molecules described as precursors of tRNA in pulse-chase experiments were found. The syntheses of stable methylated LMW RNAs, different from tRNA, were also shown. The sizes of these molecules, determined by their migration in polyacrylamide gels, were 5.3S; 5.8S; 6.3S and 6.9S These RNAs resemble the nuclear LMW RNAs, discovered in different animal cells, in infertilized eggs and developing embryos of sea urchin among them. The data obtained allow one to suppose an existance of a maturation stage during formation of these RNAs. The synthesis of a certain fraction of LMW RNAs (4.9S) was sensible to low doses of alpha-amanitin and therefore involved RNA-polymerase II.
Mol Biol (Mosk)
PMID:[Properties of different classes of low molecular weight RNAs]. 75 88

The evolution of 5sRNA of 17 organisms ranging from human to bacteria has been studied using a sequence homology analysis. The evolutionary rate of 5sRNA genes has been estimated to be 2.2x10(-10) replacement per one nucleotide site per year. This value is about the same as that of cytochrome C or tRNA's (congruent to 2x10(-10)). A phylogenic tree of these organisms including both eukaryotes and prokaryotes has been constructed from the evolutionary distances (the rate of nucleotide substitution per site) data. The time of divergence of prokaryotes and eukaryotes was estimated to be greater than or congruent to 1.75x10(9) years ago and the branching order in eukaryotic kingdoms is consistent with the traditional order. Blue-green algae separated from the bacterial stem greater than or congruent to 1.3x10(9) years ago after eukaryotes had branched.
J Mol Evol 1975 Dec 31
PMID:Evolution of 5sRNA. 76 86

The work described in this paper was done to see whether the partial suppression of temperature-sensitive aminoacyl-tRNA synthetase mutations by ribosomal mutations is restricted to the aminoacyl-tRNA synthetase mutation which was used for the selection of the suppressor strains or whether the ribosomal mutations can also suppress mutations of other aminoacyl-tRNA synthetases. It is shown that a mutation in ribosomal protein S5 which was selected for suppression of an alanyl-tRNA synthetase mutation (alaS-3) can also partially compensate the temperature-sensitivity of two valyl-tRNA synthetase mutants and of another alanyl-tRNA synthetase mutant. Furthermore, revertants of a temperature-sensitive valyl-tRNA synthetase mutant were isolated and screened for alterations in ribosomal proteins by electrophoretic and immunochemical methods. Alterations in at least two proteins, S8 and S20, were clearly observed among the mutants. The alteration in protein S8 renders the growth of this strain severely cold-sensitive. Presence of the mutation in protein S8 is strictly correlated with suppression of temperature-sensitivity. The S8 mutation maps between strA and spc on the Escherichia coli chromosome. Five suppressor strains have quantitatively or qualitatively altered ribosomal proteins S20. In one strain no S20 protein could be detected at all, employing different electrophoretic and immunological methods. All five suppressor mutations map in the thr-leu region of the E. coli chromosome, i.e. in an area where the alteration of protein S20 in two alaS suppressor strains has been localized previously.
Mol Gen Genet 1975 Dec 09
PMID:Alteration of ribosomal proteins in revertants of a valyl-tRNA synthetase mutant of Escherichia coli. 76 30

The mode and site of action of inhibitors of translation (initiation, elongation and termination of protein synthesis) in eukaryotic systems is reviewed. The isolation and characterization of a factor is described that binds Ac-Phe-tRNA to form a complex made up of binding factors, Ac-Phe-tRNA, and ribosome. The binding of Ac-Phe-tRNA probably occurs at the ribosomal site involved in the binding of the initiator substrate Met-tRNAF. The effect of inhibitors of the intitiation phase of protein synthesis on the nonenzymic Ac-Phe-tRNA binding to ribosomes is investigated. The two sites translocation model for translation in eukaryotic cells is presented and the effects of inhibitors on the various steps of protein synthesis are determined empirically. The site of action of inhibitors of peptide bond formation at the ribosomal peptidyl transferase center is elucidated. The action of inhibitors of translocation is sutdied in model cell-free systems from human cells. In addition, a number of methylxanthines are shown to enhance the elongation phase in polypeptide synthesis by stimulating the enzymic binding of aminoacyl-tRNA. The effect of caffeine, theophylline and its derivatives are shown to be fairly specific and dependent on the ribosome concentration. Aminophylline is shown to have a similar effect but also enhances aminoacyl-tRNA synthetase activity at low Mg++ concentrations, probably displacing the optimal concentration of Mg++ in the reaction. This second effect of aminophylline appears to be due to the ethylenediamine moiety of aminophylline since it is also observed in the presence of different polyamines but not in the presence of caffeine or theophylline.
Mol Cell Biochem 1976 Feb 16
PMID:Antibiotics and compounds affecting tanslation by eukaryotic ribosomes. Specific enhancement of aminoacyl-tRNA binding by methylaxnthines. 76 41

Yeast tRNAPhe has been modified by excising the Y base and by replacing the Y base or the dihydrouracil residue with the fluorescent dyes proflavine or ethidium bromide. The poly(U) directed ribosomal system from E. coli was used to study the activities of the tRNAPhe derivatives in the assays for ribosome binding and polyphenylalanine synthesis. It was found that the tRNAPhe derivatives modified by replacing dihydrouracil were nearly as active as unmodified tRNAPhe. While excision of the Y base led to a considerable decrease in the activities, replacement by the above mentioned dyes yielded rather active tRNAPhe derivatives. The activities decreased somewhat when the tRNAPhe derivatives with a substitution in the anticodon loop were reduced with NaBH4. The lower plateau values observed with some of the tRNAPhe derivatives are largely attributed to a decreased efficiency of tRNA binding to the ribosomes which, in turn, results in an increased susceptibility to deacylation prior to phenylalanine transfer.
Mol Biol (Mosk)
PMID:[Characterization of fluorescent derivatives of tRNA Phe by experiments in the ribosomal system]. 76 43

The kinetics of the affinity modification of phenylalanyl-tRNA synthetase from E. coli MRE-600 with chb-tRNA was used for investigation of copling between the binding sites of tRNA and other ligands. It was shown that ATP, phenylalanine and their mixture do not change the efficiency of complex formation but decrease specifically the rate of enzyme alkylation. L-Tyrosine and L-valine do not influence the enzyme alkylation. ATP is more effective protector than L-phenylalanine. In the presence of both ATP and phenylalanine the enzyme alkylation is excluded. The possibilities of this method for studying the coupling between binding sites are discussed.
Mol Biol (Mosk)
PMID:[Affinity modification of phenylalanyl-tRNA-synthetase in the presence of ligands]. 77 90

Binding of oxytetracycline to E. coli ribosomes was studied by equilibrium dialysis. The results are consistent with the existence of two classes of binding sites for the antibiotic on ribosomes having different reactivities. There is one strong binding site as well as about 500 weak ones. The association constant for strong complexes is about 10(3) times greater than the value for weak ones. Oxytetracycline and tetracycline bind to ribosomes as magnesium chelates. Increase of the concentration of Mg2+ leads to the formation of two types of magnesium chelates of the antibiotic: chelate 1 which is formed at a relatively low concentration of Mg2+ and has a stiochiometry 1:1, and chelate 2 which probably corresponds to the attachment of second ion to the antibiotic molecule. The strong binding of oxytetracycline to ribosomes prevents the template dependent association of aminoacyl-tRNA with ribosomes. However, no changes in the extent of the antibiotic binding were found upon addition of aminoacyl-tRNA, poly(U) and chloramphenicol to oxytetracycline-ribosome complexes. It has been suggested that inhibiting effect of oxytetracycline on the protein synthesis involves an allosteric mechanism.
Mol Biol (Mosk)
PMID:[Oxytetracycline binding to E. coli ribosomes]. 77 91


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