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M Laughrea

Publications and source records attributed to M Laughrea.

At least 37 records · Page 2Linked to original sources
PubMed1988

The poly(U) translational capacity of Fischer 344 rat liver does not deteriorate with age and is not affected by dietary regime.

The translational capacity of ribosomes isolated from the livers of young (60-170 days, n = 13) and old (26.5 months, n = 11) Fischer 344 rats was assessed by poly(U)-directed [3H]phenylalanine incorporation. Run-off ribosomes and S100 supernatant were separately prepared from each individual liver. Ribosome concentrations were carefully measured. Individual differences were seen among young rats and among old rats; however, when considered as a group, the old rats, whether diet-restricted or fed ad libitum, translated poly(U) as well, or almost as well, as the young ones.

Aging↗
PubMed1987

Mistranslation in twelve Escherichia coli ribosomal proteins. Cysteine misincorporation at neutral amino acid residues other than tryptophan.

The misincorporation of cysteine (codon: UGU/C) into twelve ribosomal proteins devoid of cysteine has been studied. Although it is generally assumed that cysteine is misincorporated at arginine and tryptophan residues (codons: CGU/U and UGG respectively), our results are consistent with the idea that cysteine is also misincorporated at phenylalanine residues (codon: UUU/C) through a second-position C:U mismatch. Cysteine was found in ribosomal proteins L29, L32/L33 and S10, under conditions where only its misincorporation at neutral residues was measured. Since these proteins contain no tryptophan, the date imply that cysteine has replaced a neutral amino acid other than tryptophan. Because there was a statistically significant correlation between the total level of cysteine in the twelve proteins under study and their content of phenylalanine and arginine residues, we conclude that there is a likelihood of cysteine misincorporation at phenylalanine residues, in addition to its misincorporation at arginine and tryptophan residues. Our measurements are consistent with the existence of a cluster of ribosomal proteins having an average mistranslation frequency of 2.5 X 10(-4)/residue and another having an average mistranslation frequency of 10(-3)/residue. There was three times less cysteine misincorporated into ribosomal protein L1 than into L7/L12, although the L1 mRNA contains eleven CGU/C codons and four UUU/C codons while the L7/L12 mRNA contains only one arginine and two phenylalanine codons (both proteins are free of tryptophan). Furthermore, the mRNAs for both L1 and L7/L12 contain a CGU codon located in the context GUA-codon-GG and there was as much cysteine incorporated at this codon in L7/L12 [Bouadloun, F., Donner, D. and Kurland, C.G. (1983) EMBO J. 2, 1351-1356] than in the whole of L1. This suggests that, relatively speaking, little cysteine is to be found at the phenylalanine and the other ten arginine positions of L1 and that the phenylalanine residues of L7/L12 are particularly error-prone.

Amino Acids↗
PubMed1985

Translation fidelity in the aging mammal: studies with an accurate in vitro system on aged rats.

The accuracy of poly(U) translation was measured in the post-mitochondrial supernatant from whole brain of 7- and 33-month-old Fischer 344 rats. Measurements were made: under in vitro conditions in which translation fidelity was similar to what is known about the accuracy of translation in vivo; and under stresses of varying Mg2+ concentrations (3-12 mM), pH (6.6-8.4), temperature (26-42 degrees C) and in the presence or absence of 2.4% ethanol. No significant difference could be detected between the responses of old and young extracts, the activities of their Phe- and Leu-tRNA synthetases, and their endogenous amounts of Phe-tRNA and Leu-tRNA, despite the fact that the rats studied corresponded in age (by actuarial criteria) to 90-year-old human beings. The accuracy of poly(U) translation was also studied: in liver and hippocampus extracts from 7- and 33-month-old rats; and in brain extracts from 3- and 29-month-old rats. The results were similar to those obtained in brain extracts from 7-month-old rats. Explanations are provided for the inconsistencies which exist in the literature regarding the effect of aging on the accuracy of protein synthesis. It is shown that the inconsistencies are likely to reflect inadequate methodology in three previous studies rather than biological diversity in the control of translation fidelity in aged animals.

Aging↗
PubMed1984

Effect of ethanol, phenol, formamide, dimethyl sulfoxide, paromomycin, and deuterium oxide on the fidelity of translation in a brain cell-free system.

The effects of six different agents (ethanol, phenol, formamide, dimethyl sulfoxide, heavy water, and a misreading-inducing antibiotic, paromomycin) on the activity and the accuracy of poly(U) translation have been compared under a range (2.5-12 mM) of Mg2+ concentrations in a rat brain cell-free system. The effect of most of these agents was remarkably sensitive to the Mg2+ concentration under which the assay was made. Ethanol decreased the fidelity of translation, and the efficiency of ethanol was increased 3-10-fold by higher Mg2+ concentrations. The effect of paromomycin was identical with that of ethanol, despite its very different structure. Formamide, a "RNA denaturant", increased the accuracy of translation under all Mg2+ concentrations tested. Dimethyl sulfoxide, another type of RNA denaturant, decreased the accuracy of translation under all Mg2+ concentrations tested. Phenol increased the accuracy of translation at high Mg2+ concentrations but decreased it at low Mg2+ concentrations. D2O did not change to any appreciable extent the accuracy of translation, at all the Mg2+ concentrations used. There exists a cooperativity between the effects of Mg2+ and ethanol, Mg2+ and paromomycin, and Mg2+ and dimethyl sulfoxide on the fidelity of translation; no such cooperativity was detected between Mg2+ and formamide and between Mg2+ and D2O. The differential effects of dimethyl sulfoxide and formamide are interpreted in terms of their different dielectric constants. The dielectric constant of dimethyl sulfoxide is higher than that of water, while that of formamide is low er.

Animals↗
PubMed1984

Comparative analysis of translation accuracy in an Escherichia coli and a mammalian cell-free system.

The effect of environmental stress on the accuracy of protein synthesis in an Escherichia coli and a rat brain cell-free system was investigated. Poly-U was translated in a rat brain and an E. coli cell-free extract under identical ionic conditions. The fidelity of translation, both in the E. coli and the rat brain extracts, was commensurate with what is known about the accuracy of translation in vivo. The incorporation of phenylalanine (code: UUU) and leucine (code: CUU, UUG or A) was measured at various Mg2+ concentrations (3 to 22 mM), various pH's (6.6 to 8.6), various temperatures (23 to 42 degrees C), and in the presence or absence of 2.4% (v/v) ethanol. It was observed that (i) the accuracy of translation was generally higher in extracts from E. coli than from rat brain, and (ii) relative to that in E. coli, the translation fidelity in rat brain extracts was about 2 times more sensitive to ethanol, at least 5 times more sensitive to temperature, and at least 50 times more sensitive to pH. It was found that this differential sensitivity was not due to a differential behavior of the bacterial and the mammalian aminoacyl-tRNA synthetases under stress, but rather to the process of chain elongation itself. It is concluded that the accuracy of protein synthesis is more resistant to environmental stress in E. coli extracts than in extracts from at least one mammalian tissue.

Amino Acyl-tRNA Synthetases↗
PubMed1982

Transfer ribonucleic acid dependent but ribosome-independent leucine incorporation into rat brain protein.

An unusual type of posttranslational modification has been observed in a rat brain in vitro system. It consists in leucine addition to a preformed protein in such a way that the added leucine is not located at either the NH2 or the COOH terminus of the acceptor protein. The incorporation reaction requires ATP, ATP-generating components and tRNA. It is inhibited by aurintricarboxylic acid but does not require the presence of ribosomes or GTP. The incorporated leucine has a free NH2 group, and it is not released by leucine aminopeptidase or carboxypeptidase A. It is linked to the acceptor protein through a bond that is too alkali labile and too hydroxylamine labile to be a peptide bond. The simplest interpretation of the results consists in proposing that an ester bond is formed between the leucine and the side chain of a serine, threonine, or tyrosine in the acceptor protein.

Adenosine Triphosphate↗
PubMed1981

Speed-accuracy relationships during in vitro and in vivo protein biosynthesis.

Poly U-directed incorporation of phenylalanine and leucine into polypeptide has been described in at least 50 papers since 1961. In general, high translation activities are associated with high accuracies, and vice-versa. Moreover, a vast body of independent experimental data (effect of ethanol, temperature, urea, aminoglycosides, etc... on protein synthesis) put together here suggests that, in many circumstances, speed and accuracy of elongation are correlated. This result is to be contrasted with the view that the speed and the fidelity of protein synthesis are two opposing parameters. In this report, recent experimental data on the nature and effect of ribosomal ambiguity (ram) and streptomycin resistance (Strr) mutations are reexamined. Models on the action of streptomycin and other misreading-inducing antibiotics, as well as long-standing ideas on the control of misreading in mammalian systems are critically evaluated. An explanation is provided for the long-befuddling data on the action of gentamicin.

Animals↗
PubMed1981

Differential effects of ethanol and the rpsL1 (strA1) ribosomal mutation on the synthesis of an unusual protein coded by bacteriophages R17 and MS2 RNA.

During translation of R17 and MS2 RNA, ethanol stimulates the synthesis of a coat-related protein which has identical electrophoretic mobility to that of polypeptide 7 studied by Atkins and his colleagues. Streptomycin stimulates the synthesis of this polypeptide and broadens the protein band. In contrast the ribosomal protein S12 mutation rpsL1 (strA1) has no detectable effect on its synthesis.

Coliphages↗
PubMed1979

The conformational properties of ribosomal protein S1.

The proton NMR spectrum of S1 reveals that S1 has considerable tertiary structure in physiological buffers, but more structural flexibility than normal for globular proteins. S1's NMR spectrum is independent of the method of preparation.

Carbonic Anhydrases↗
PubMed1978

X-ray and neutron small-angle scattering studies of the complex between protein S1 and the 30-S ribosomal subunit.

X-ray neutron solution scattering experiments have been done to investigate the influence of the binding of ribosomal protein S1 on the conformation of the 30-S ribosomal subunit of Escherichia coli. The following conclusions were made. 1. The alterations (if any) in conformation of the non-S1 parts of the 30-S subunit induced by S1 binding are too small to be detected (less than 0.1 nm change in radius of gyration). 2. The center of gravity of protein S1 bound to the 30-S subunit is quite far from the center of gravity of the particle (approximately 7.5 nm).

Escherichia coli↗