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Biomedical subjects

L Brakier-Gingras

Publications and source records attributed to L Brakier-Gingras.

52 records · Page 3Linked to original sources
PubMed1983

The 60S ribosomal subunit is altered in the skeletal muscle of dystrophic hamsters.

Polysomes from the skeletal muscle of normal and dystrophic hamsters were dissociated into ribosomal subunits by treatment with puromycin and the subunits from both strains were reassociated in all possible combinations. When their protein synthesis activity was assayed in a poly(U)-directed cell-free system at a low magnesium concentration, the reassociated ribosomes from dystrophic hamsters were less active than the ribosomes from control animals. The ribosomal defect is a property of the 60S subunit and is due to a ribosomal component rather than to abnormal binding of a non-ribosomal protein.

Animals↗
PubMed1983

Characterization of mutants of Escherichia coli with an increased control of translation fidelity.

Neomycin-resistant mutants of Escherichia coli K12 were selected on a minimal succinate medium containing neomycin. In an in vitro poly(U)-dependent protein synthesizing assay, the ribosomes from the mutant strains showed lower levels of misreading than wild-type ribosomes in the presence of neomycin or other error-promoting aminoglycoside antibiotics or ethanol. The mutation was shown to affect a component of the 30S subunit and to facilitate the dissociation of ribosomes into subunits. It is suggested that an impairment in the subunit interaction may be responsible for the observed restriction of the stimulation of misreading.

Drug Resistance, Microbial↗
PubMed1983

A ribosomal defect in dystrophic hamsters.

Polysomes were isolated from the skeletal muscle, the heart, and the liver of dystrophic and normal hamsters and their protein synthesis activity was assessed in a cell-free wheat germ extract as a source factors and tRNAs. Our results show that there is a shift of the optimal magnesium concentration required for protein synthesis with polysomes from the skeletal muscle and the heart of dystrophic hamsters, as compared with control hamsters. As a consequence of this shift, polysomes from the skeletal muscle and the heart of dystrophic hamsters, were less active than normal ones at low magnesium concentrations, but more active at high magnesium concentrations. These changes in activity were age dependent since, with skeletal muscle, they were observed at 30 days and disappeared at 60 days but reappeared at 120 and 200 days. With heart polysomes, on the other hand, the changes in activity were observed at 60 days but not in younger or older animals. No change in activity was observed with liver polysomes. Similar results were obtained when endogenous mRNAs were replaced by an exogenous messenger such as poly(U). This suggests that the differences in protein synthesis activity between polysomes from dystrophic and normal hamsters are not due to changes in the endogenous mRNAs but result from a ribosomal abnormality.

Animals↗
PubMed1982

Effect of neomycin and protein S1 on the binding of streptomycin to the ribosome.

The binding of [3H]dihydrostreptomycin to the 70-S ribosome or to the 30-S subunit has been investigated in the presence of neomycin by the Millipore filtration or the equilibrium dialysis procedure. It was observed that dihydrostreptomycin binds equally well to the 30-S subunit and the 70-S ribosome, and that neomycin stimulates the binding of dihydrostreptomycin to the ribosome by increasing the association constant and not by creating new binding sites. Specific removal of protein S1 from the 30-S subunit neither affected the binding of dihydrostreptomycin to the ribosome nor the stimulation of dihydrostreptomycin binding by neomycin.

Binding Sites↗
PubMed1981

Comparison of the misreading induced by streptomycin and neomycin.

In a poly(U)-programmed translation system, neomycin stimulates the misincorporation of tyrosine and of serine which, according to Thompson and Stone (Thompson, R.C. and Stone, P.J. (1977) Proc. Natl. Acad. Sci. USA. 74, 198-202), are normally rejected at an initial discrimination step during the binding of charged tRNAs to the ribosome. In contrast, streptomycin favors the misincorporation of isoleucine which is normally rejected at a subsequent GTP-dependent discrimination step, the so-called proofreading step. The labeling of the ribosome with N-ethylmaleimide mimics the effect of streptomycin in that it stimulates the misincorporation of isoleucine but not of tyrosine or serine. This effect is correlated with the labeling of protein S18 but not with that of protein S1. These observations indicate that the sulfhydryl group of protein S18 is located within a ribosomal domain involved in the proofreading control of tRNA selection. Taking into account our previous results that streptomycin and neomycin perturb ribosomal areas around the sulfhydryl groups of proteins S18 and S1, respectively, we suggest that these antibiotics induce misreading by different mechanisms which are linked to such perturbations.

Escherichia coli↗
PubMed1980

Comparison of the action of streptomycin and neomycin on the structure of the bacterial ribosome.

The influence of streptomycin and neomycin upon the conformation of the ribosome has been investigated using spin-labeled and fluorescent analogs of the sulfhydryl reagent, N-ethylmaleimide. Changes in the electron paramagnetic resonance spectra or in the polarization of fluorescence of labeled ribosomes reveal that streptomycin alters the mobility of labels bound to the sulfhydryl group of protein S18 while neomycin affects the mobility of labels bound to the sulfhydryl groups of proteins S1, S21 and/or L10. It is also observed that both streptomycin and neomycin interfere with changes in the mobility of labels induced by storage under inactivating conditions. From these results, it is concluded that: 1. streptomycin and neomycin distort the conformation of the ribosome at different sites, streptomycin disturbing preferentially the area around the sulfhydryl group of protein S18 while neomycin affects the environment of the sulfhydryl groups of proteins S1, S21 and/or L10; 2. streptomycin and neomycin interefere with the ability of the ribosome to undergo conformational changes.

Edetic Acid↗
PubMed1979

Decrease in the rate of protein synthesis by polysomes from cultured fibroblasts of patients and carriers with Duchenne muscular dystrophy.

Polysomes extracted from cultured fibroblast cells isolated from patients with Duchenne muscular dystrophy (DMD), carriers of the disease, and normal controls were used for in vitro measurement of protein synthesis in a wheat germ extract system. It was observed that polysomes from patients and carriers (seven of each aged 17 years or older) exhibited a 3-fold and a 1.5-fold decrease in the rate of protein synthesis, respectively, as compared with controls. These results are discussed with a view to developing a sensitive and easily available assay for the detection of DMD carriers.

Adolescent↗
PubMed1978

Streptomycin-induced conformational changes in the 70-S bacterial ribosome.

Conformational alterations induced by streptomycin in the bacterial ribosome have been investigated using as probes, ethidium bromide, N-[14C]ethylmaleimide and a spin label nitroxide analog of N-ethylmaleimide. 1. The binding of the antibiotic to the ribosome does not affect the reactivity of sulfhydryl groups towards N-ethylmaleimide. 2. The motional freedom of spin labels bound to ribosomal proteins S1 and S18 is increased but it is hardly affected at other labeled sites. This observation suggests that the binding of streptomycin causes a local loosening of the ribosomal structure. 3. Ribosomes are found to bind less ethidium bromide in the presence of streptomycin, which suggests that the binding of streptomycin decreases the degree of organization of ribosomal RNA.

Electron Spin Resonance Spectroscopy↗
PubMed1977

The role of misrepair processes in the isolation of new types of streptomycin-resistant mutants in Escherichia coli.

Treatment of Escherichia coli cells with ethylmethanesulfonate followed by a prolonged delay for phenotypic expression allows to select new types of streptomycin-resistant mutants, which are double mutants with one change resulting from base mispairing and the second one from misrepair. The error-prone recA-dependent pathway is involved in this misrepair, as evidenced by the fact that recA strains do not provide double mutants.

DNA Repair↗
PubMed1976

New types of streptomycin-resistant mutants of Escherichia coli.

Mutagenesis of Escherichia coli K12 cells with ethyl methanesulfonate and selection of streptomycin-resistant mutants after a long delay for phenotypic expression allowed us to isolate new types of streptomycin-resistant ribosomes. Misreading patterns of the ribosomes in the presence of streptomycin revealed that most of the streptomycin-resistant mutants isolated under these conditions differed from the four classical types of streptomycin-resistant mutants studied and characterized by Strigini, P. and Gorini, L. (1970) J. Mol. Biol. 47, 517-530.

Coliphages↗
PubMed1976

The use of N-succinyl derivatives in the study of amino acids and peptides by mass spectrometry.

The terminal amino group of amino acids and peptides is blocked as the N-succinyl derivative by reaction with succinic anhydride. The product is then converted to the N,O-permethyl derivative in order to increase its volatility for use in mass spectrometry. The permethylated N-succinyl derivative retains the advantages of the permethylated N-acetyl derivative in regard to ease of preparation on a small scale, volatility and the presence of characteristic fragmentation patterns in their mass spectra. However, peaks in the high mass region are more abundant due to loss of CH3O-from the N-succinyl carbomethoxyl group as well as from the C-terminal carbomethoxyl group. Ions characteristic of the sequence and of individual amino acids are observed, and molecular weight can be determined from the relatively abundant ion at [M--CH3O]+ and from the weak molecular ion.

Amino Acids↗
PubMedDate not supplied

Pleiotropic effects of mutations at positions 13 and 914 in Escherichia coli 16S ribosomal RNA.

Mutations at position 13 or 914 of Escherichia coli 16S ribosomal RNA exert pleiotropic effects on protein synthesis. They interfere with the binding of streptomycin, a translational miscoding drug, to the ribosomes. They increase translational fidelity, and this effect can be related to a perturbation of the higher order structure of the 530 stem-loop, a key region for tRNA selection. In contrast, the structure of the decoding center is not perturbed. The mutations also affect translational initiation, slowing down the formation of the 30S initiation complex. This effect can be related to a destabilization of the pseudoknot helix (17-19/916-918), at the convergence of the three major domains of 16S ribosomal RNA.

Base Sequence↗