Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “tRNA”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45Linked to original sources
PubMed1995

Interaction of 5SrRNA-L5 protein complex, methionyl-tRNA, and methionyl-tRNA synthetase in the macromolecular ARS complex.

Rat liver cytosol was incubated with a trace amount of rat liver 5SrRNA which was highly labeled at the 3'-end with cytidine 3',5'-[5'-32P]biphosphate, and with [35S]methionine in the presence of ATP mixture, and then with an antibody against ribosomal protein L5. The mixture was analyzed by protein A-Sepharose chromatography. The following results were obtained. (i) The eluate with glycine-HCl buffer (pH 3.0) from the protein A-Sepharose column contained an overlapping peak of 32P- and 35S-radioactivities. In a control experiment using the same amount of 32P-labeled Escherichia coli 5SrRNA with the same specific activity, no fraction of the eluate contained 32P-radioactivity. (ii) The fractions containing both 32P- and 35S-radioactivities from the protein A-Sepharose column were crosslinked by UV irradiation. The products was subjected to PAGE, and RNA in each gel slice was eluted and purified. The fraction containing both 32P- and 35S-radioactivities was present in a region of somewhat higher molecular weight than that of 5SRNP, whereas very low 32P- and 35S-radioactivities were present in this region in the control experiment without UV irradiation. This finding suggested that [35S]methionyl-tRNA interacted with 32P-labeled 5SRNP. (iii) The fraction containing overlapping 32P- and 35S-radioactivities described above was subjected to Sephadex G-150 chromatography. The component containing both radioactivities was distributed in the region corresponding to molecular weights of 10,000 to 250,000 with a peak at about 200,000, suggesting the presence of a complex containing Met-RS (Mr 108,000), 5SRNP (Mr 74,000), and methionyl-tRNA (Mr 25,000). Furthermore, this fraction showed definite Met-RS activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acyl-tRNA Synthetases↗
PubMed1979

Lack of correlation between affinity of the tRNA for the aminoacyl-tRNA synthetase and aminoacylation capacity as studied with modified tRNAPhe.

The interactions of several modified yeast tRNAPhe [tRNAPhe lacking 7-methylguanine; a fragment comprising about 3/4 of the whole molecule: tRNAPhe (18--76); tRNAPhe (18--76) lacking 7-methylguanine] with yeast phenylalanyl-tRNA synthetase were studied. Upon excision of the 5'-quarter of the tRNAPhe molecule, the residual fragment still tightly binds to the synthetase, but can no longer by aminoacylated. Surprisingly, upon removal of the 7-methylguanine base at position 46 in this fragment, althought the affinity drops by a factor 10, a significant aminoacylation is restored. These results are discussed in terms of molecular flexibility and a model is proposed for tRNA-enzyme interaction, involving multisite recognition.

Amino Acyl-tRNA Synthetases↗
PubMed1983

Activity patterns of aminoacyl-tRNA synthetases, tRNA methylases, arginyltransferase and tubulin: tyrosine ligase during development and ageing of Caenorhabditis elegans.

As a step in the characterization of development and ageing in the nematode Caenorhabditis elegans, the activities of different groups of enzymes that supposedly exert modulating functions in and after protein synthesis have been determined. From embryonic (E), the four juvenile larval stages (L1-L4) and the gravid adult (A,A+), the selection of defined developmental stages extends to two different preparations of aged nematodes (S10, S12). Some aminoacyl-tRNA synthetase activities remain nearly unchanged in all stages up to the adult, some increase continuously during the larval stages and the remaining activities show stage-specific alterations. Upon ageing all activities except the one for tryptophan decrease sharply, tRNA methylase activities increase from E to L4, decrease from L4 to adult and to aged nematodes with only qualitative alterations in substrate specificity. The activity of tubulin: tyrosine ligase exhibits a parallel pattern, while arginyltransferase activity has a plateau between L2 and L4. The results are consistent with the idea of a modulation of protein synthesis and other cellular processes by quantitative activity changes during development and ageing.

Acyltransferases↗
PubMed1987

Isoleucyl-tRNA synthetase from baker's yeast and from Escherichia coli MRE 600. Discrimination of 20 amino acids in aminoacylation of tRNA(Ile)-C-C-A(3'NH2).

For discrimination between isoleucine and the other 19 naturally occurring amino acids by isoleucyl-tRNA synthetases from baker's yeast and from Escherichia coli MRE 600 discrimination factors have been determined from kcat and Km values in aminoacylation of the modified tRNA(Ile)-C-C-A(3'NH2). Discrimination factors D1 are products of an initial discrimination factor and a proof-reading factor: D1 = I1.II1. From discrimination factors and AMP formation stoichiometry factors I1 and II1 were calculated. D1 values obtained with the enzyme from E. coli are generally higher than those observed with the yeast enzyme, in some cases up to ten times. With both enzymes low D1 values are found for cysteine, valine, and tryptophan (20-200), the highest values for glycine, alanine, and serine (600-4000). I1 values calculated for the E. coli enzyme are slightly higher (4-145) than the factors observed with the yeast enzyme (1-85), proof-reading factors II1 of the E. coli enzyme are scattering about a mean value about 70, those of the yeast enzyme about a mean value about 50. Initial discrimination factors I1 are directly related to hydrophobic interaction forces between the substrates and the enzymes. Plots of Gibbs free energy differences calculated from these factors are linearly related to the accessible surface areas of the amino acids. A hypothetical model of the binding site can be given in which selection of amino acids is achieved by hydrophobic forces and removal of steric hindrance.

Acylation↗
PubMed1986

Participation of the dnaK and dnaJ gene products in phosphorylation of glutaminyl-tRNA synthetase and threonyl-tRNA synthetase of Escherichia coli K-12.

The heat shock proteins DnaK and DnaJ of Escherichia coli participate in phosphorylation of both glutaminyl-tRNA synthetase and threonyl-tRNA synthetase. When cellular proteins extracted from the dnaK7(Ts) and dnaJ259(Ts) mutant cells labeled with 32Pi at 42 degrees C were analyzed by two-dimensional gel electrophoresis, no phosphorylation of these proteins was observed when they were compared with those from wild-type cells.

Amino Acyl-tRNA Synthetases↗
PubMed1990

Nonprotein amino acid furanomycin, unlike isoleucine in chemical structure, is charged to isoleucine tRNA by isoleucyl-tRNA synthetase and incorporated into protein.

Nonprotein amino acid furanomycin was found to bind with Escherichia coli isoleucyl-tRNA synthetase (IleRS) almost as tightly as the substrate L-isoleucine. The conformation of furanomycin bound to the enzyme was determined by NMR analyses including the transferred nuclear Overhauser effect method. The conformation of IleRS-bound furanomycin was similar to that of L-isoleucine, although the chemical structure of furanomycin is unlike that of L-isoleucine. By E. coli IleRS, E. coli tRNAIle was charged with furanomycin as efficiently as with L-isoleucine. Furthermore, furanomycyl-tRNAIle was bound to polypeptide chain elongation factor Tu as tightly as isoleucyl-tRNAIle. Furanomycin was found to be incorporated into beta-lactamase precursor by in vitro protein biosynthesis. A newly designed amino acid will probably be incorporated into proteins, provided that the new amino acid takes a similar conformation as a protein-constituting amino acid in the active site of an aminoacyl-tRNA synthetase.

Amino Acids↗
PubMedDate not supplied

[Chemical modification of phenylalanyl-tRNA synthetase and ribosomes of Escherichia coli with derivatives of tRNA-Phe carrying photoreactive groups on guanosine residues].

Photoreactive derivatives of tRNAPhe (E. coli) were synthesized by alkylation of the tRNAPhe with 4-(N-2-chloroethyl-N-methylamino)benzylamine and subsequent treatment with 1.4--dinitro-5-fluorophenylazide. The derivatives are active in binding with ribosomes and phenylalanyl-tRNA synthetase when the extent of modification is lower than 3 reactive groups per tRNAPhe molecule. Under irradiation the derivatives modify exclusively the beta-subunit of the phenylalanyl-tRNA synthetase.

Amines↗
PubMedDate not supplied

[Alkylation of tRNA-Phe free and bound to phenylalanyl-tRNA synthetase with 4-(N-2-chloroethyl-N-methylamino)benzylamine].

Reactivities toward the alkylating reagent 4-(N-2-chloroethyl-N-methylamino)benzylamine of guanosine residues in the tRNAPhe free and bound to the phenylalanyl-tRNA synthetase were determined. This highly efficient reagent modifies mainly guanosine in single-stranded as well as in helical regions of tRNAs. The reaction is sensitive to the elements of the macrostructure of tRNAs. It is found the phenylalanyl-tRNA synthetase protects the D-stem of the tRNAPhe (guanosines G10, G22, G24) from alkylation.

Alkylation↗
PubMed1993

Crystals of the phenylalanyl-tRNA synthetase from Thermus thermophilus HB8 complexed with tRNA(Phe).

Phenylalanyl-tRNA synthetase (EC 6.1.1.20) from the extreme thermophile Thermus thermophilus HB8 has been crystallized with its cognate tRNA. Compared with the native crystals, the crystals of the complex are more stable to radiation damage and diffract to 3.0 A resolution. They are of space group P3(2)21, with a = b = 175 A, c = 142.1 A, gamma = 120 degrees, almost identical with the crystal parameters of the native synthetase.

Crystallization↗
PubMed1992

Crucial role of pyrophosphate in the aminoacylation of E. coli tRNA(Phe) by yeast phenylalanyl-tRNA synthetase.

Rapid inactivation of the yeast phenylalanyl-tRNA synthetase in the course of aminoacylation of the heterologous E. coli tRNA(Phe) is observed. This inactivation occurs due to the formation of the tight complex of the enzyme with the pyrophosphate formed during the aminoacylation reaction. This complex is shown to be the normal intermediate of the reaction. Possible inactivation mechanism and correlation between structural differences of yeast and E. coli tRNAs(Phe) with the changes in the enzymatic mechanism of aminoacylation are discussed.

Acylation↗
PubMed1991

The interaction of wheat germ tyrosyl-tRNA synthetase and the tRNA-like end of brome mosaic virus RNA has no effect on in vitro viral protein synthesis and on in vitro encapsidation.

The effect of aminoacylation of the tRNA-like end of brome mosaic virus RNA during in vitro protein synthesis and in vitro viral encapsidation was investigated. The components of the homologous system were: BMV RNA, wheat germ cell-free protein synthesizing system and pure tyrosyl-tRNA synthetase from wheat germ. During in vitro protein synthesis directed with tyrosylated as well as non-tyrosylated BMV RNA, no differences were observed in the amount and in the class of polypeptides formed neither in the velocity of the translation reaction. Excess active TyrRS was added during in vitro translation, without modifying the translation efficiency. BMV RNA and active TyrRS were preincubated prior to translation in order to interact without the translation system components and then subjected to translation in vitro. Similar results were obtained when BMV RNA was preincubated with inactive TyrRS or BSA. These results indicate that the aminoacylation of BMV RNA has no pronounced effect on viral protein synthesis in vitro. During BMV RNA encapsidation either tyrosylated or non-tyrosylated BMV RNA 4 could be encapsidated in a similar way.

Capsid↗
PubMed1998

A pseudoknotted tRNA variant is a substrate for tRNA (cytosine-5)-methyltransferase from Xenopus laevis.

tRNA post-transcriptional modification enzymes of Xenopus laevis were proposed previously to belong to two major groups according to their sensitivity to structural perturbations in their substrates. To further investigate the structural variations tolerated by these enzymes, the tRNA-like domain of turnip yellow mosaic virus RNA (88 nucleotides in length) has been microinjected into the oocytes of Xenopus laevis. This RNA possesses 12 potential target nucleotides for modification within a structure including a pseudoknotted folding, an extended anticodon stem, and unusual D-loop/T-loop interactions. Results indicate that only cytosine-42, a position equivalent to C-49 in canonical tRNAs, was quantitatively modified into m5C in the microinjected RNA. Modification was detected to high levels, indicating that at least one enzyme tolerates non-canonical structural features.

Animals↗
PubMed1998

A conserved domain within Arc1p delivers tRNA to aminoacyl-tRNA synthetases.

Two yeast enzymes that catalyze aminoacylation of tRNAs, MetRS and GluRS, form a complex with the protein Arc1p. We show here that association of Arc1p with MetRS and GluRS is required in vivo for effective recruitment of the corresponding cognate tRNAs within this complex. Arc1p is linked to MetRS and GluRS through its amino-terminal domain, while its middle and carboxy-terminal parts comprise a novel tRNA-binding domain. This results in high affinity binding of cognate tRNAs and increased aminoacylation efficiency. These findings suggest that Arc1p operates as a mobile, trans-acting tRNA-binding synthetase domain and provide new insight into the role of eukaryotic multimeric synthetase complexes.

Amino Acyl-tRNA Synthetases↗
PubMed2005

Structure and activity of an aminoacyl-tRNA synthetase that charges tRNA with nitro-tryptophan.

The most divergent of two tryptophanyl tRNA synthetases (TrpRS II) found in Deinococcus radiodurans interacts with a nitric oxide synthase protein that produces 4-nitro-tryptophan (4-NRP). TrpRS II efficiently charges transfer RNA(Trp) with 4-NRP and 5-hydroxy-tryptophan (5-HRP). The crystal structures of TrpRS II bound to tryptophan and 5-HRP reveal residue substitutions that accommodate modified indoles. A class of auxiliary bacterial TrpRSs conserve this capacity to charge tRNA with nonstandard amino acids.

5-Hydroxytryptophan↗
PubMed2000

Characterization and tRNA recognition of mammalian mitochondrial seryl-tRNA synthetase.

Animal mitochondrial protein synthesis systems contain two serine tRNAs (tRNAs(Ser)) corresponding to the codons AGY and UCN, each possessing an unusual secondary structure; the former lacks the entire D arm, and the latter has a slightly different cloverleaf structure. To elucidate whether these two tRNAs(Ser) can be recognized by the single animal mitochondrial seryl-tRNA synthetase (mt SerRS), we purified mt SerRS from bovine liver 2400-fold and showed that it can aminoacylate both of them. Specific interaction between mt SerRS and either of the tRNAs(Ser) was also observed in a gel retardation assay. cDNA cloning of bovine mt SerRS revealed that the deduced amino acid sequence of the enzyme contains 518 amino acid residues. The cDNAs of human and mouse mt SerRS were obtained by reverse transcription-polymerase chain reaction and expressed sequence tag data base searches. Elaborate inspection of primary sequences of mammalian mt SerRSs revealed diversity in the N-terminal domain responsible for tRNA recognition, indicating that the recognition mechanism of mammalian mt SerRS differs considerably from that of its prokaryotic counterpart. In addition, the human mt SerRS gene was found to be located on chromosome 19q13.1, to which the autosomal deafness locus DFNA4 is mapped.

Amino Acid Sequence↗
PubMed1999

Relationship of the CCA sequence of tRNA with the early evolutional aspect of aminoacyl-tRNA synthetases.

The CCA sequence is common to the 3'-ends of all tRNAs. We investigated the requirement of the CCA sequence in aminoacylation with the cognate aminoacyl-tRNA synthetases (aaRSs) and several interesting conclusions could be drawn. In tRNAs belonging to the class I aaRSs, decreased aminoacylation activities resulted from the substitution of A76 with a pyrimidine, whereas in tRNAs belonging to the class II aaRSs, decreased aminoacylation activities resulted from the substitution with guanine. The results suggest that aminoacylation of proto-tRNA might have started through the direct hydrophobic (or stacking) interaction between the large, hydrophobic amino acid residue (now utilizing a class I aaRS) of aminoacyl-AMP and the 3'-terminal adenine. The shorter distance between the adenine and the 2'-OH position than the 3'-OH position, and the bulkiness and hydrophobicity of amino acids may be important reasons why class I aaRSs select the 2'-OH position in aminoacylation. Molecular mechanics-based conformation modeling also indicated that the resulting positioning of the adenine and the amino acid residue of 2'-aminoacyl-adenosine for large amino acid is in the vicinity. In contrast, in the case of small amino acids (with class II aaRSs) which would not be able to use the hydrophobic interaction, a protein enzyme might have participated in the aminoacylation reaction from an early stage. The active-site folds of aaRSs belonging to each class reflect the history of evolution: typical nucleotide-binding fold (Rossman fold) in the case of class I aaRSs, and primitive fold which is found also among the family of nonribosomal peptide synthetases in the case of class II aaRSs.

Amino Acyl-tRNA Synthetases↗