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M Renaud

Publications and source records attributed to M Renaud.

At least 55 records · Page 3Linked to original sources
PubMed1982

Affinity labelling of yeast phenylalanyl-tRNA synthetase with a 3'-oxidised tRNAPhe. Isolation and sequence of the labelled peptide.

Yeast phenylalanyl-tRNA synthetase was specifically labelled with a 3'-oxidised tRNAPhe. Stoichiometric inactivation was achieved with the incorporation of 2 mol oxidised tRNA Phe/mol enzyme which corresponds exactly to the stoichiometry of tRNA binding. The labelled peptide has been isolated using a quick chromatographic procedure which can be applied to any covalent complex formed between a tRNA and an aminoacyl tRNA synthetase. The isolated peptide (18 amino acids) was found to encompass the unique cysteine sequence of the smaller beta subunit of the enzyme.

Affinity Labels↗
PubMed1982

Conformational activation of aminoacyl-tRNA synthetases upon binding of tRNA. A facet of a multi-step adaptation process leading to the optimal biological activity.

The activation of the catalytic center of aminoacyl-tRNA synthetases upon binding of the tRNA, previously reported in the case of yeast phenylalanyl-tRNA and valyl-tRNA synthetases [Renaud et al., (1981) Proc. Natl Acad. Sci. USA, 78, 1606-1608] has been investigated in other systems. It is shown that this property is encountered not only in cognate systems (phenylalanyl, valyl and arginyl) but also in the non-cognate systems which are particularly efficient in misaminoacylation reactions. The arginyl system, the peculiarity of which is to form the aminoacyladenylate only in the presence of the cognate tRNA, is shown to be a border-line case of this general process of catalytic center activation. In the case of the phenylalanyl system, the crucial role of the wybutine residue (adjacent to the anticodon) in the activation of phenylalanyl-tRNA synthetase by the tRNA core has been analysed by comparison with native or modified non-cognate tRNAs (tRNATyr, tRNAArg). It is proposed that upon complex formation between a tRNA and its cognate aminoacyl-tRNA synthetase, a multistep adaptation process takes place in order to promote the optimal rate for the aminoacylation reaction, thus contributing to the specificity of this reaction.

Adaptation, Biological↗
PubMed1981

Study of the interaction between yeast tRNAphe and yeast phenylalanyl-tRNA synthetase by monochromatic ultraviolet irradiation at various wavelengths. Advantages and limits of the method.

The interactions between yeast tRNAphe and phenylalanyl-tRNA synthetase were studied by analysis of the covalent adducts obtained upon monochromatic ultraviolet irradiation at different wavelengths (248, 282, 292, 302 and 313 nm). The high extent of inactivation of phenylalanyl-tRNA synthetase, together with the partial modification of tRNA, as well as the peculiar instability of most of the covalent bonds formed upon irradiation constitute severe limitations to the use of the technique and to the interpretation of the results. These disadvantages led us to select an irradiation wavelength of 248 nm and to use only mild isolation procedures allowing a good recovery of the covalent adducts formed. Seven major tryptic peptides of the enzyme were found to be cross-linked to tRNAPhe whereas six major T1-oligonucleotides were covalently linked to the protein, among these, the three cross-linked oligonucleotides previously described by Shoemaker and Schimmel (J. Biol. Chem. 250 (1975) 4440-4444) in the same system. The difference in the number of covalently linked oligonucleotides is discussed in the light of the instability of the covalent linkages. The localization of the six oligonucleotides at the inside of the two branches forming the L-shaped tRNA molecule is similar to that observed in the yeast valine system (Renaud et al., Eur. J. Biochem. 101 (1979) 475-483) and is consistent with the interaction model previously described (Rich and Schimmel, Nucl. Acids Res. 4 (1977) 1649-1665 and Ebel et al. in Transfer RNA: structure, properties and recognition, (1979) pp. 325-343 Cold Spring Harbor Laboratory, NY). The occurrence of covalent cross-linking upon irradiation in the tryptophan absorption band (302 nm) strongly suggests the participation of this residue in the stabilization of the tRNA enzyme complex.

Amino Acyl-tRNA Synthetases↗
PubMed1981

[Amyloidosis-a dreaded complication of juvenile chronic arthritis (JCA). (author's transl)].

Our studies describe symptoms, clinical course and prognosis of 60 children (out of a total of 2063 patients) suffering from chronic arthritis complicated with amyloidosis. Amyloidosis is predominantly caused by the systemic subgroup of juvenile chronic arthritis, which is characterized by high inflammation activity. The amyloidosis and the sequelae are one of the main causes of death in JCA (27 of the 90 lethal cases in our juvenile chronic arthritis unit were connected with amyloidosis). Proteinuria is the most frequent sign in the early stage of the amyloidosis. Early diagnose and treatment by cytostatic drugs like chlorambucil seems to improve the prognosis. The cumulative survival results in the existence of two different subgroup of amyloidosis.

Adolescent↗
PubMed1981

Conformational activation of the yeast phenylalanyl-tRNA synthetase catalytic site induced by tRNAPhe interaction: triggering of adenosine or CpCpA trinucleoside diphosphate aminoacylation upon binding of tRNAPhe lacking these residues.

Adenosine or CpCpA trinucleoside diphosphate can be aminoacylated by phenylalanyl-tRNA synthetase [L-phenylalanine:tRNAPhe ligase (AMP forming), EC 6.1.1.20] when the reaction takes place in the presence of tRNAPhe deprived of its 3' adenosine or pCpCpA terminus. This shows that, upon interaction with tRNA, a structural alteration of the enzyme's active site is achieved. This process may be a determining step in the specificity of the aminoacylation reaction.

Adenosine↗
PubMed1981

Fluorimetric study of yeast tRNAPheCCF in the complex with phenylalanyl-tRNA synthetase. Evidence for a correlation between the structural adaptation of both macromolecules and the appearance of the acylation activity.

The fluorescence properties of yeast tRNAPheCCF (tRNAPhe in which the 3'-terminal adenosine has been replaced by formycin) and tRNAPheCCFoxi-red (tRNAPheCCF after periodate oxidation followed by borohydride reduction) were studied in the complex with the cognate aminoacyl-tRNA synthetase. In both cases a conformational change affecting the 3' end was observed in a magnesium concentration range close to 1 mM. The modification of formycin fluorescence could be ascribed simultaneously to the existence of a tautomeric equilibrium of the fluorescent probe and to a pH effect raising from a prototropic effect at the active site of phenylalanyl-tRNA synthetase, and to a partial destacking of the 3'-formycin from the adjacent C residue. The observed transconformation, which can be related to the structure modification of the anticodon loop previously reported [Ehrlich, Lefèvre, and Remy (1980) Eur. J. Biochem. 103, 145-153], takes place in the magnesium concentration range allowing the transfer of the activated amino acid from the adenylate to the tRNA. The interconnection between the anticodon loop and the accepting end was further supported by the observation that wybutine excision hinders the specific structure modification of 3'-formycin upon binding to the synthetase. The tRNAPhe transconformations occurring in the complex with the cognate synthetase probably reflect a reciprocal adaptation of both macromolecules which might lead to the optimal aminoacylation velocity and thus contribute to the specificity of aminoacylation, since it was previously established that this specificity relies more strongly on the kinetics of the reaction than on a discrimination of tRNAs according to different affinities.

Amino Acyl-tRNA Synthetases↗
PubMed1980

Practice settings and prescribing profiles: the simulation of tension headaches to general practitioners working in different practice settings in the Montreal area.

The purpose of this study was to determine whether physicians practicing in one type of setting manage a medical problem differently than those practicing in another type of setting. The investigation took the form of presenting physicians with a simulated case of tension headache with a history going back three years, for which diazepam had been taken daily for the past year. Four simulated patients (aged 20-23) visited a stratified random sample of 111 general practitioners practicing in health centers funded by government (CLSCs) and in private group practice clinics in the Montreal area. Fifty-one per cent of group practice physicians recommended therapy rated as "inadequate" compared to 25 per cent in CLSCs; in addition, the data show significant differences between CLSC and group practice physicians in performing various aspects of the clinical examination. Alternative explanations for the observed differences are discussed.

Adult↗
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↗
PubMed1979

[Oral contraception with an associated therapeutic action using a progestational method at two levels (author's transl)].

The authors, basing their work on their experience over many years with a large number of cases, are proposing that synthetic progestational agents can be used at two levels of dosage, to serve as contraception and as a treatment when a progestational agent is used and is followed by micro-dosages of another progestational substance. So they prescribe at the end a of cycle following different dosages for different lengths of time, the same (or a different) progestational agent to treat breast troubles or menstrual troubles which are often intricate, particularly near the menopause. The authors in this way can compare by trials the effects of this method as compared with those of a progestational contraceptive administered in high doses and prescribed in an interrupted way and the prescription of micro-dosages of progestational agents that are taken "non-stop" which is now a classical method of treatment. This new method of contraception using progestational agents at two levels of dosage is particularly useful in patients who cannot take oestrogens because of metabolic upsets or because of tumours and who have reacted badly to the two other methods mentioned. If the dose, which can be calculated thanks to our knowledge of the hormonal background of the patient, is altered good therapeutic results and a relatively sure method of contraception is evolved without metabolic risks for the patient. This association of two progestational levels of dosage seems to be indicated particularly in women of over 40 years of age.

Adult↗