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Query: UNIPROT:Q96FX7 (tRNA)
 26,753 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of cAMP and varying concentrations of potassium (18-72 mM) on the incorporation of L-14C-leucine into TCA-precipitable protein was studied in a cell-free system comprising rough thyroid microsomes. cAMP (2mM) alone or in combination with theopylline increased the incorporation of leucine into ribosome-bound (after DOC treatment) and extra-vesicular material, but had no significant effect on the DOC-released intravesicular material. Increase of the K+ concentration from 18 mM to 72 mM affected the incorporation of leucine into the microsomal compartments in much the same way as cAMP did. The effect of cAMP and potassium seems to be due in partly to enhanced activation of amino acids, since in a system of pH5 fraction and cell sap, both cAMP and K+ increased the incorporation of 14C-leucine into cold TCA-precipitable material. Experiments with 14C-leucyl-tRNA as a marker suggest that the effect of cAMP and K+ is a consequence not only of increased activation of amino acids, but also of increased binding of activated amino acyl-tRNA to ribosomes.
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PMID:Action of cyclic adenosine 3',5' monophosphate on L-14C-leucine incorporation in a system of rough microsomes from bovine thyroid gland. 17 65

The molecular mechanism of thermal unfolding of E. coli tRNAGlu, tRNAfMet and tRNAPhe (in 0.02M Tris-HC1, pH 7.5. 10 MM Mg C12) has been examined by the spin-labeling technique. The rate of tumbling of the spin label has been measured as a function of temperature for ten different selectively spin-labeled tRNAs. Only spin labels at position s4U-8 were able to probe the tertiary structure. Evidences are presented which support the hypothesis that the thermal denaturation of the three species of tRNAs studied is sequential. The unfolding process occurs in three discrete stages. The first step (30 degrees-32 degrees) could either be assigned to a localized reorganization of the cold-denatured structure or to a "transient" melting, followed by the simultaneous disruption of the tertiary structure and part of the hU helix. This transition is observed even in the absence of magnesium. The second step (50 degrees-54 degrees) involves the melting of the anticodon and miniloop regions. The last step occurs above 65 degrees where the t psi c and amino acid acceptor stems, forming one continuous double helix, melt. A simple dynamic model is considered for tRNA function in protein biosynthesis.
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PMID:A spin label study of the thermal unfolding of secondary and tertiary structure in E. colic transfer RNAs. 17 54

In order to find new genetic loci and functions on the yeast mitochondrial DNA, especially mutations affecting the mitochondrial protein synthesis apparatus, temperature sensitive mutants have been isolated after MnCl2 mutagenesis and mitochondrial and nuclear mutants classified according to their pattern of recombination with three rho- tester strains. Eighteen cold- and heat-sensitive respiratory deficient mitochondrial mutants have been isolated and localized on the mitochondrial genome by deletion mapping using 113 rho- strains. Eight of them appear to represent new loci, among which some are probably mutations of the tRNA and rRNA genes.
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PMID:Temperature-sensitive respiratory-deficient mitochondrial mutations: isolation and genetic mapping. 32 84

This compilation presents in a small space the tRNA sequences so far published in order to enable rapid orientation and comparison. The numbering of tRNAPhe from yeast is used as has been done earlier (1) but following the rules proposed by the participants of the Cold Spring Harbor Meeting on tRNA 1978 (2) (Fig. 1). This numbering allows comparisons with the three dimensional structure of tRNAPhe, the only structure known from X-ray analysis. The secondary structure of tRNAs is indicated by specific underlining. In the primary structure a nucleoside followed by a nucleoside in brackets or a modification in brackets denotes that both types of nucleosides can occupy this position. Part of a sequence in brackets designates a piece of sequence not unambiguously analyzed. Rare nucleosides are named according to the IUPAC-IUB rules (for some more complicated rare nucleosides and their identification see Table 1); those with lengthy names are given with the prefix x and specified in the footnotes. Footnotes are numbered according to the coordinates of the corresponding nucleoside and are indicated in the sequence by an asterisk. The references are restricted to the citation of the latest publication in those cases where several papers deal with one sequence. For additional information the reader is referred either to the original literature or to other tRNA sequence compilations (3--7). Mutant tRNAs are dealt with in a separate compilation prepared by J. Celis (see below). The compilers would welcome any information by the readers regarding missing material or erroneous presentation. On the basis of this numbering system computer printed compilations of tRNA sequences in a linear form and in cloverleaf form are in preparation.
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PMID:Compilation of tRNA sequences. 42 82

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.
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PMID:Genetical studies on revertants to sensitivity from a cycloheximide resistant strain of Schizosaccharomyces pombe. 67 2

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.
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PMID:Alteration of ribosomal proteins in revertants of a valyl-tRNA synthetase mutant of Escherichia coli. 76 30

One hundred and seventy seven pieces of normal or pathologic thyroid tissue from 17 patients were assayed for rRNA, tRNA and DNA content. The tRNA/DNA and rRNA/DNA ratios in pathologic tissue were statistically compared with the same ratios in normal tissue. In toxic adenoma (5 cases) and anoplastic cancer (2 cases), both ratios were increased. In cold nodules (9 cases), there was in increase of the tRNA/DNA ratio only in 1 case, of the rRNA/DNA ratio only in 4 cases, and of both ratios in 3 cases. In one case of a cold nodule in a Basedow's disease gland, there was no modification of these ratios. In Basedow's disease (3 cases), there was an increase of rRNA/DNA ratio only in one case.
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PMID:Ribosomal and transfer RNA contents of the normal and pathologic human thyroid gland. 92 18

1. It was found that preincubation of the reaction mixture in the cold enhanced polyuridylic acid-directed polyphenylalanine synthesis by a cell-free extract of Thermus thermophilus HB8 at high temperature. 2. The effect of preincubation was most marked at 10-25 degrees in the presence of 20 mM Mg2+. Preincubation at 65 degrees failed to stimulate the incorporation. 3. The presence of phenylalanyl-tRNA, polyuridylic acid, and ribosomes was essential for preincubation in the cold to be effective. 4. A ternary complex of amino acyl-tRNA, polyuridylic acid, and a ribosome formed at low temperature was isolated by CPG-10 column chromatography; the isolated complex initiated polyphenylalanine synthesis effectively at high temperature. 5. The amount of the ternary complex formed depends on the preincubation time and the concentration of Mg2+. Since the amount of the complex correlated positively to the rate of polyphenylalanine synthesis at high temperature, the effectiveness of preincubation in the cold is presumably due to the formation of the ternary complex of phenylalanyl-tRNA, polyuridylic acid, and a ribosome.
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PMID:Protein synthesis in a cell-free system from an extreme thermophile. Effects of preincubation in the cold on polyuridylic acid-dependent polyphenylalanine synthesis at high temperature. 95 53

Patterns of RNA synthesis using tritiated uridine were studied in organ cultures of mouse embryonic limb cartilage and epiphyseal cartilage from mice 5 days of age. The cold phenol-sodium dodecyl sulfate extracted RNA was characterized by methylated albumin kieselguhr chromatography and polyacrylamide gel electrophoresis. The general pattern of synthesis indicates the persistence of primarily low molecular weight tRNA and a diminishing synthesis of rRNA in the older cartilage. Data show that the increased radioactivity in the low molecular weight fraction is not due to the accumulation of rRNA breakdown products. These findings are discussed in relation to other age-related studies on RNA biosynthesis.
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PMID:Changes in the pattern of RNA synthesis in mouse limb cartilage during early development. 95 5

Cultured mouse L-cells, pulse labeled for 5 min with 3H-uridine, were gently suspended in 0.5mM cupric sulfate and 0.5% sodium dodecyl sulfate at 4 degrees C and treated with cold phenol. Only the RNA, containing less than 1% DNA, was extracted by this procedure. The rapidly labeled ribosomal RNA precursors (44S, 34S) and cytoplasmic 8S RNA showed specific activities higher than that of tRNA and were present in the RNA fraction insoluble in 2M NaCl.
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PMID:Isolation of rapidly labeled RNA from mouse L-cells using cupric sulfate. 117 61


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