Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RIBOSOMES”

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 649 records · Page 36Linked to original sources
PubMedDate not supplied

[Nature of the heterogeneity of the 30S ribosomal subunits in vitro. II. Two types of inactivation of the 30S subunits of Escherichia coli ribosomes].

The influence of concentration of monovalent cations on the binding constant of Phe-tRNAPhe to 30S.poly(U) complex was studied. Two types of inactivation of the 30S subunits by ammonium ions at the low magnesium concentration (1 mM) were found. The first type of inactivation was observed at high concentrations of NH4+ ions (from 0.5 to 1.5 M) and due to the dissociation of ribosomal proteins from 30S subunits. This inactivation only decreased the binding constant of Phe-tRNAPhe to 30S.poly(U) complex up to 50 times but all 30S subunits were equally achieved in Phe-tRNAPhe binding. This type of inactivation was reversible, addition of S-proteins restored the association constant to the original value. At low concentration of NH4+ ions (below 100 mM) about half of the 30S subunits is irreversibly inactivated (the binding constant of Phe-tRNAPhe decreased below detectable level) probably as a result of conformational changes in ribosomal RNA. Both types of inactivation of the 30S subunits can take place during the preparation of isolated subunits of ribosomes.

Escherichia coli↗
PubMedDate not supplied

[Ribosomal proteins interacting with Phe-tRNAPhe during enzymatic binding with translating ribosome before and after the release of the elongation factor EF-Tu].

Proteins, directly interacting with tRNA in R- and A-sites of E. coli ribosome were determined by means of ultraviolet-induced RNA-protein cross-links. It is shown, that tRNAPhe in the R-site (upon enzymatic binding of the ternary complex Phe-tRNAPhe. X Tu X GMPPCP to ribosome) directly interact with factor Tu and ribosomal proteins S4, S5, S8 and L6, while in the A-site (upon binding of Phe-tRNAPhe X Tu X GTP, GTP hydrolysis, Tu release and transpeptidation)--with proteins S5, S10, L6, L16 and S13/S14/L27.

Escherichia coli↗
PubMed1979

Identification by affinity chromatography of the eukaryotic ribosomal proteins that bind to 5.8 S ribosomal ribonucleic acid.

The proteins that bind to rat liver 5.8 S ribosomal ribonucleic acid were identified by affinity chromatography. The nucleic acid was oxidized with periodate and coupled by its 3'-terminus to Sepharose 4B through and adipic acid dihydrazide spacer. The ribosomal proteins that associate with the immobilized 5.8 S rRNA were identified by polyacrylamide gel electrophoresiss: they were L19, L8, and L6 from the 60 S subunit; and S13 and S9 from the small subparticle. Small amounts of L14, L17', L18, L27/L27', and L35', and of S11, S15, S23/S24, and S26 also were bound to the affinity column, but whether they associate directly and specifically with 5.8 S rRNA is not known. Escherichia coli ribosomal proteins did not bind to the rat liver 5.8 S rRNA affinity column.

Animals↗
PubMed1983

Specific visualization of ribosomal RNA in the intact ribosome by electron spectroscopic imaging.

The recently developed electron microscopic technique of electron spectroscopic imaging has been used to map the distribution of phosphorus, and therefore of RNA, in situ in the ribosomal subunits of E. coli. The results indicate that the RNA moiety of both subunits is concentrated toward the centre of the particle somewhat more than is the total mass, but reaches the outer surface at several places. The micrographs also reveal certain distinctive features in the shape of the RNA component that may be related to the overall shape of the ribosome. The method yielded a reasonably accurate estimate of the phosphorus content of the 30 S ribosome.

Microscopy, Electron↗
PubMed1980

Identification by affinity chromatography of the rat liver ribosomal proteins that bind to Escherichia coli 5 S ribosomal ribonucleic acid.

The eukaryotic and prokaryotic ribosomal proteins that bind to Escherichia coli 5 S rRNA were identified by affinity chromatography. The E. coli ribosomal proteins that associated with the nucleic acid were L5, L18, and L25 confirming earlier findings using the same and different procedures. The rat liver ribosomal proteins that associated with E. coli 5 S rRNA were L6, L7, L19, L35a, and S9; several of those proteins also bind to rat liver 5 S rRna (L6, L19) and to 5.8 S rRna (L6, L19, and S9).

Animals↗
PubMed1982

The primary structure of the acidic phosphoprotein P2 from rat liver 60 S ribosomal subunits. Comparison with ribosomal 'A' proteins from other species.

The primary structure of rat liver ribosomal protein P2 was deduced from the sequence of the peptides. Ten peptides were obtained by cleavage of P2 with trypsin. The peptides, which accounted for the 111 residues of P2, were isolated by high voltage electrophoresis and chromatography on cellulose thin layer sheets, and the partial or complete sequence was determined by micromanual or solid-phase procedures using 4-N,N-dimethylaminoazobenzene 4'-isothiocyanate and phenylisothiocyanate. In a similar manner, the sequence of 14 peptic peptides was determined. The sequence of the NH2-terminal 30 residues of P2 was obtained by automatic Edman degradation in a sequenator. The ordering of the tryptic peptides was aided by determination of the partial or complete sequence of fragments generated with chymotrypsin, or Armillaria mellea protease, or by secondary cleavage of peptic peptides with trypsin. The carboxyl-terminal sequence was obtained from a cyanogen bromide fragment and from hydrolysis with carboxypeptidase. The sequence of protein P3 was also determined. P3 differs from P2 only in that it lacks the carboxyl-terminal 8 residues, and hence, it is likely to be a proteolytic product of P2. Rat liver ribosomal protein P2 is homologous with yeast YP A1, with Artemia salina eL12, and with Halobacterium cutirubrum L20. It is likely that rat liver P2 is also homologous with the prokaryotic ribosomal "A" proteins, Escherichia coli L7/L12, Micrococcus lysodeikticus MA1, and Bacillus subtilis L9, but that during evolution, a transposition of a portion of the molecule occurred.

Amino Acid Sequence↗
PubMed1980

Characterization of the binding of rat liver ribosomal proteins L6, L7, and L19 to 5 S ribosomal ribonucleic acid.

The binding of rat liver ribosomal proteins L6, L7, and L19 to 5 S rRNA was characterized by nitrocellulose membrane filtration. Binding could be saturated with the three proteins; the apparent association constants (Ka'), measured at 4 degrees C and 22 degrees C, ranged from 1.3 to 6.8 x 10(5) M-1. The molar ratio of ribosomal protein and rRNA in the complex at saturation approximated 1, indicating there is one binding site for each of the three proteins on the nucleic acid. A large number of rat liver ribosomal proteins, including some previously suspected of associating weakly, did not form a complex with 5 S rRNA.

Animals↗
PubMed1993

Phosphorylation of acidic ribosomal proteins by ribosome-associated protein kinases of Saccharomyces cerevisiae and Schizosaccharomyces pombe.

Two proteins of 13 kDa and 38 kDa, the components of 60S ribosomal subunits, were identified as phosphorylation substrates for protein kinases tightly associated with S. cerevisiae and Schizosaccharomyces pombe ribosomes. An enzyme with properties of multifunctional casein kinase II was detected in ribosome preparations from both yeast species. In S. cerevisiae another protein kinase with high substrate specificity toward those proteins was also identified. By using isoelectric focusing, the protein band of 13 kDa from S. cerevisiae and S. pombe was resolved respectively into three and four major forms of different charge. The same protein forms were phosphorylated in the in vivo 32P-labelling experiments.

Amino Acid Sequence↗
PubMed2000

Protein-ribosome-mRNA display: affinity isolation of enzyme-ribosome-mRNA complexes and cDNA cloning in a single-tube reaction.

An enzyme-ribosome-mRNA complex was specifically purified by binding to the immobilized enzyme substrate and the cDNA was cloned in a single-tube reaction by one-step reverse transcription-PCR. The ganglioside GM3, used by sialyltransferase II (ST-II) as a substrate, was coated on a 96-well microtiter plate and ST-II was in vitro transcribed and translated from a cDNA library. The isolation of an enzyme-specific protein-ribosome (PRIME) complex was achieved with as little as 0.1 ng ST-II-specific cDNA in 5 microg of a total plasmid preparation or with the cDNA prepared from sublibraries previously inoculated at a density of 2000 clones/culture well. The affinity purification of the PRIME complex was highly specific for GM3 and did not result in cDNA amplification when a different ganglioside (GM1) was used for coating of the microtiter plate. The amplified cDNA was used for cloning or a second round of ribosome display, providing a fast analysis of enzyme affinity to multiple substrates. PRIME display can be used for host-free cDNA cloning from mRNA or cDNA libraries and for binding site mapping of the in vitro translated protein. The use of a single-tube reaction in ligand-coated microtiter plates indicates the versatility of PRIME display for cDNA cloning by automated procedures.

Chromatography, Affinity↗
PubMed1989

Presence in the stroma of chloroplasts of a large pool of a ribosomal protein not structurally related to any Escherichia coli ribosomal protein.

A search was made for the presence of a pool of free ribosomal proteins in the stroma of the spinach chloroplast. The results showed that a relatively large amount of one protein, CS-S5, is present in the stroma. Immunoprecipitation experiments showed that this protein is encoded by the nuclear genome. Clones were isolated from a cDNA library constructed in the expression vector lambda gt11, using specific antibodies raised against the CS-S5 protein. A full-length cDNA was sequenced which contains an open reading frame (ORF) for the precursor of the CS-S5 protein, as shown by immunoprecipitation. This precursor contains a putative transit peptide of 66 amino acids and the mature product has no significant homology with any of the Escherichia coli ribosomal proteins, in contrast to the other ribosomal protein gene products so far identified in spinach chloroplasts.

Amino Acid Sequence↗
PubMed1977

Chromosome location of the ribosomal RNA genes in Triturus vulgaris meridionalis (Amphibia, Urodela). II. Intraspecific variability in number and position of the chromosome loci for 18S + 28S ribosomal RNA.

Ribosomal genes have been localized on mitotic and lampbrush chromosomes of 20 specimens of Triturus vulgaris meridionalis by in situ hybridization with 3H 18S + 28S rRNA. The results may be summarized as follows: 1) each individual shows positive in situ hybridization at the nucleolus organizing region (NOR) on chromosome XI; 2) in addition, many specimens exhibit a positive reaction in chromosomal sites other than the NOR (additional ribosomal sites); 3) the chromosomal distribution of the additional sites appears to be identical in different tissues from the same specimen and to follow a specific individual pattern; 4) the additional ribosomal sites are preferentially found at the telomeric, centromeric or C-band regions of the chromosomes involved.

Animals↗
PubMed1990

Yeast ribosomal proteins: XI. Molecular analysis of two genes encoding YL41, an extremely small and basic ribosomal protein, from Saccharomyces cerevisiae.

Two genes encoding ribosomal protein YL41 were cloned from Saccharomyces cerevisiae chromosomal DNA. Both genes contain an uninterrupted region of only 75 nucleotides coding for a protein of 3.3 kD. Within the coding regions the nucleotide sequences are virtually identical, whereas in both the 5'- and 3'-flanking regions the two genes differ significantly from each other. The deduced protein shows an arginine and lysine content of 68 percent, i.e., 17 out of 25 residues, and the basic residues are evenly distributed over the molecule. When compared to the ribosomal protein sequences currently available no counterpart to YL41 could be found in prokaryotes and it seems likely that YL41 is a eukaryote-specific ribosomal protein.

Amino Acid Sequence↗
PubMed1975

Ribosome run through of the termination codon in the absence of the ribosome releasing factor.

The ribosome releasing factor (RR factor) which releases ribosomes from mRNA at the termination codon has been examined for its effects on the amino acid incorporation programmed by wild type R17 Phage RNA and amB2 R17 RNA. When RR factor was added at the beginning of the incorporation, there was no effect on the initial rate of incorporation but it reduced the final level of incorporation. The reduction of the final level of incorporation was more pronounced for histidine incorporation than for valine incorporation suggesting that the translation of the RNA polymerase cistron was more influenced by RR factor. These experiments were carried out under conditions where no reinitiation of protein synthesis occurred. In the presence of RR factor, suppressor tRNA functioned better for the incorporation of amino acids into proteins with amB2 R17 RNA than did wild type tRNA. No such differential effect of suppressor tRNA was observed in the absence of RR factor. This suggests that the ribosome has to be released from mRNA by RR factor in order for the amber mutation to be effective.

Codon↗
PubMed1988

Amino acid sequences of ribosomal proteins S11 from Bacillus stearothermophilus and S19 from Halobacterium marismortui. Comparison of the ribosomal protein S11 family.

The complete amino acid sequences of ribosomal proteins S11 from the Gram-positive eubacterium Bacillus stearothermophilus and of S19 from the archaebacterium Halobacterium marismortui have been determined. A search for homologous sequences of these proteins revealed that they belong to the ribosomal protein S11 family. Homologous proteins have previously been sequenced from Escherichia coli as well as from chloroplast, yeast and mammalian ribosomes. A pairwise comparison of the amino acid sequences showed that Bacillus protein S11 shares 68% identical residues with S11 from Escherichia coli and a slightly lower homology (52%) with the homologous chloroplast protein. The halophilic protein S19 is more related to the eukaryotic (45-49%) than to the eubacterial counterparts (35%).

Amino Acid Sequence↗
PubMed1987

Mechanism of ribosomal translocation. tRNA binds transiently to an exit site before leaving the ribosome during translocation.

Escherichia coli ribosomes have a site (E) to which deacylated tRNA binds transiently before leaving the ribosome during translocation. The affinity of the site is Mg2+ dependent and low at physiological Mg2+ concentrations. Correct codon-anticodon interaction is unnecessary in this site. With these features, the E site cannot reduce frameshift errors through additional mRNA anchorage. Occupancy of the A site does not influence the tRNA binding in the E site, although a conformational change of elongation factor G, brought about by GTP hydrolysis, is necessary for efficient tRNA release. The tRNA can dissociate unhindered from the E site when the elongation factor is bound to the ribosome by fusidic acid. During elongation, the thermodynamically stable state is not attained, since E site occupation inhibits translocation. However, the E site can aid elongation by providing an intermediate state for tRNA dissociation, dispersing the process into more than one step.

Allosteric Site↗
PubMed1977

Spacer transfer RNAs in ribosomal RNA transcripts of E. coli: processing of 30S ribosomal RNA in vitro.

At least three different transfer RNAs are produced by in vitro processing of 30S ribosomal RNA which accumulates in RNAase III- strains of E. coli. Two of these tRNAs, tRNAGlu2 and tRNAIle1, have previously been shown to be "spacer tRNAs"--that is, genes for their synthesis are located in rRNA transcription units between the cistrons for 16S and 23S rRNAs (Lund et al., 1976). The third tRNA whose sequences are contained in 30S rRNA is tRNAAla1B. In addition to the tRNAs, 5S rRNA and several other 4S fragments are produced. Some of these 4S fragments may represent additional spacer tRNAs. One fragment, about 70 nucleotides long, arises from the 5' end of the 17S precursor of 16S rRNA. Four or five other tRNAs are hydrogen-bonded to 30S rRNA as we prepare it; one or more of these tRNAs may also be a spacer tRNA. The enzymes that process tRNAs out of 30S rRNA are associated with ribosomes, but can be removed from them by washing in 0.2 M NH4Cl; the enzymes required for 5S rRNA processing remain bound to the 0.2 M NH4Cl-washed ribosomes. Treatment of 30S rRNA with purified RNAase III produces 6-8S fragments which contain the sequences of tRNAGlu2, tRNAAla1B and 5S rRNA.

Base Sequence↗
PubMed2006

The highly conserved LepA is a ribosomal elongation factor that back-translocates the ribosome.

The ribosomal elongation cycle describes a series of reactions prolonging the nascent polypeptide chain by one amino acid and driven by two universal elongation factors termed EF-Tu and EF-G in bacteria. Here we demonstrate that the extremely conserved LepA protein, present in all bacteria and mitochondria, is a third elongation factor required for accurate and efficient protein synthesis. LepA has the unique function of back-translocating posttranslocational ribosomes, and the results suggest that it recognizes ribosomes after a defective translocation reaction and induces a back-translocation, thus giving EF-G a second chance to translocate the tRNAs correctly. We suggest renaming LepA as elongation factor 4 (EF4).

Amino Acid Sequence↗