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M Grunberg-Manago

Publications and source records attributed to M Grunberg-Manago.

At least 109 records · Page 6Linked to original sources
PubMed1980

Characterization of Mg2+-induced conformational change in the 50S ribosomal subunit by differential hydrogen exchange.

The technique of differential hydrogen exchange allows detection of a conformational change in the 50S subunit of Escherichia coli ribosome when the magnesium concentration is lowered in a range where ribosomal activity is fully preserved. This change is characterized by a seventy-fold acceleration of about thirty labile hydrogens in the case of a Mg2+ jump from 10 mM to 2 mM. The small number of hydrogens involved can explain the difficulty in detecting this change by other methods.

Escherichia coli↗
PubMed1980

Physical localisation and cloning of the structural gene for E. coli initiation factor IF3 from a group of genes concerned with translation.

The structural genes for translational initiation factor IF3, threonyl-tRNA synthetase (TRS), the two subunits of phenylalanyl-tRNA synthetase (PRS), and a 12 000 mol. wt. protein of unidentified function are carried by the lambda p2 transducing phage. The localization of these genes on a restriction map of the Escherichia coli DNA insert was achieved by deletion mapping. In addition a set of plasmids carrying fragments of the original phage was constructed and helped to confirm these assignments. One plasmid, containing a 3.3 kb PstI fragment inserted into pBR322, does not code for any of the synthetase genes but causes strains carrying it to overproduce IF3.

Bacteriophage lambda↗
PubMed1980

Identification by photoaffinity labelling of 16S RNA as a component of IF2-binding site of E. coli MRE 600 ribosome.

A photoactivated radioactive derivative of IF2 was obtained by treatment with p-azidobenzaldehyde in the presence of NaBH4, followed by reductive methylation with [14C] formaldehyde. The modified IF2 preserved the functional activity of the native factor in specific binding to 30S ribosomal subparticles to which it specifically cross-linked during mild irradiation. The main affinity-labelled component of the 30S subparticle was found to be 16S RNA.

Affinity Labels↗
PubMed1979

Genetic organization of the E. coli chromosome around the structural gene for initiation factor IF3 (infC).

A set of lambda transducing phages carrying varying lengths of the E. coli chromosome around the structural gene for initiation factor IF3 (infC) was derived from lambda p2 which is known to carry, besides infC, the structural genes for the alpha subunit of phenylalanyl-tRNA synthetase (pheS), the beta subunit of phenylalanyl-tRNA synthetase (pheT) and the structural gene for threonyl-tRNA synthetase (thrS). The E. coli coding content of these derived phages was analysed by genetic complementation of a set of mutants and by SDS-polyacrylamide gel analysis of the proteins synthesized in UV irradiated cells infected with these phages. The segregation pattern of the different genes among these derived phages indicates that the order of the genes is pheT - pheS - "P12" - (infC, thrS) where infC is probably between "P12" and thrS. "P12" is the structural gene of a 12,000 molecular weight unidentified protein.

Coliphages↗
PubMed1979

Cation-induced regulatory mechanism of GTPase activity dependent on polypeptide initiation factor 2.

Initiation factor IF-2 ribosome dependent GTP hydrolysis (uncoupled GTPase) presents a bell-shaped pH profile which is shifted by changes in ionic strength. At low ionic strength (I = 25 mM) the maximal hydrolytic activity occurs at pH 7.5; when the ionic strength is increased the pH optimum of the reaction is shifted toward more acidic values. Such behavior can be satisfactorily explained as the effect of an electrostatic potential developed by a neighboring polyanion, presumably RNA, on the catalytic site. The addition of fMet-tRNAfMet or AcPhe-tRNAPhe and messenger RNA (coupled GTPase) changes the ionic strength--pH characteristics of the reaction. Thus there is an effect, direct or indirect, of components located at the ribosomal P site. Investigation of the effect of neighboring polyanions on the catalytic activity of the factor-dependent ribosomal GTPases can be seen to provide information about their functional significance that is complementary to that gained from direct structural studies.

Escherichia coli↗
PubMed1979

Recognition of tRNA Trp by initiation factors from Escherichia coli.

Binding of acetyl or formyltryptophanyl-tRNA Trp from Escherichia coli or beef liver to E. coli ribosomes is strongly stimulated by E. coli initiation factors and requires GTP. The N-acylated tryptophan is puromycin reactive. Polypeptide chain initiation with acetyltryptophan dependent on poly(U,G) has been demonstrated and is highly dependent on added initiation factors. tRNA Trp appears, therefore, to share some structural features with tRNAfMet of significance to the process of polypeptide chain initiation.

Escherichia coli↗
PubMed1978

Turbidimetric and potentiometric studies of ribosomal subunits from an erythromycin resistant mutant of Escherichia coli.

Turbidimetric and potentiometric techniques were applied to the analysis of an EryR mutant. Results show that in the mutant, the 30S subunits are drastically altered, as indicated by a higher Mg2+ requirement for subunit association and by an important difference in the titratable groups. Replacement of parental 50S by mutant 50S subunits does not decrease the association capacity with 30S parental subunits, but a structural difference is detected in the mutant 50S with potentiometric measurements. The mutation results in decreased ribosomal in vitro activities at 22 degrees C including lowered polyphenylalanine synthesis, drastic altered initiation step and the loss of erythromycin binding to the ribosomes. The results extend previous observation of a gene eryC part in the maturation of both subunits.

Drug Resistance, Microbial↗
PubMed1978

Protons and Mg2+ cations as probes in investigating the role of GTP in initiation complex formation.

fMet-tRNAfMet binding to both 30-S subunits and to 70-S particles is dependent on both pH AND Mg2+ concentration: for fMet-tRNAfMet binding to 70-S particles, variations of pH and Mg2+ concentration are tightly interdependent. This behavior can be interpreted by the polyelectrolyte theory as a direct consequence of the fact that the binding occurs in a polyanionic micro-environment. The pH-dependent binding to 70-S particles clearly shows the involvement of two prototropic groups which appear to be those carrying out GTP hydrolysis, therefore directly linked to initiation complex formation; in the presence of a non-hydrolyzable analogue to GTP, guanosine 5'-[beta, gamma-imido]triphosphate, the binding of fMet-tRNAfMet shows much less interdependence between variation of pH and Mg2+ concentration.

Binding Sites↗
PubMed1977

Thermodynamic studies of the reversible association of Escherichia coli ribosomal subunits.

The kinetics of association of Escherichia coli 30S and 50S ribosomal subunits have been carried out as a function of temperature after a magnesium jump from 1.5 to 3 mM. Turbidimetric recordings combined with a stopped-flow apparatus were used to follow the kinetics. The data show that the rates of formation and dissociation of the 70S particles at 3 mM Mg2+ and +25 degrees C were, respectively: k2 = 10(5) M-1 s-1, k1 = 4,5 X 10(-3) s-1; lowering the temperature decreases the rate constants with activation energies equal to E2 = 7.5 kcal/mol, E1 = 26.5 kcal/mol and enhances the association equilibrium towards the 70S species with an enthalpy change (delta H degrees assoc = -19.9 kcal/mol) dominant over the entropy change (delta S degrees assoc = -33 cal/(deg mol)). These thermodynamic parameters were compared to those obtained from studies on the interactions of codon-anticodon in yeast phenylalanine transfer RNA as well as of ribooligonucleotides. The kinetic and thermodynamic data are shown to be consistent with 16S-23S RNA interaction.

Binding Sites↗
PubMed1977

Characterization of an E. coli mutant with a thermolabile initiation factor IF3 activity.

A thermosensitive E. coli mutant is described which has at least two defects in vitro: a thermolabile initiation factor IF3 activity and a modified L-phenylalanine: tRNAPhe ligase (EC 6.1.1.20) activity. These two defects cotransduce and are located near 38 min on the new E. coli map. Thermoresistant revertants showing in vitro reversion for one defect also revert in vitro for the other defect. The thermosensitive mutation is recessive to its wild type allele, and in vitro analysis of wild type/ mutant heterodiploïds also show reversion for both defects.

Amino Acyl-tRNA Synthetases↗
PubMed1976

Toward an understanding of the formylation of initiator tRNA methionine in prokaryotic protein synthesis. I. In vitro studies of the 30S and 70S ribosomal-tRNA complex.

Formation of the 30S-tRNA initiation complex of Escherichia coli with nonformylated initiator tRNA is stimulated by all three initiation factors and is messenger dependent, whereas the complex formation involving the 70S ribosomes is strongly inhibited by initiation factors when the nonformylated species is used. When the 30S-Met-tRNAfMet complex is first formed and the 50S ribosomal subunit added subsequently, there is no significant inhibition by initiation factors and the nonformylated initiator tRNA is puromycin reactive. This leads to the conclusion that the formylation of the methionyl initator tRNA is only obligatory when polypeptide synthesis is initiated by nondissociated 70S ribosomes.

Binding Sites↗
PubMed1976

Toward an understanding of the formylation of initiator tRNA methionine in prokaryotic protein synthesis. II. A two-state model for the 70S ribosome.

The 70S ribosomes can select the proper initiator tRNA between Met-tRNAfMet and fMet-tRNAfMet. Experiments on binding and on formation of aminoacylpuromycin, as a function of magnesium, potassium, or initiation factors, suggest a two-state equilibrium for 70S particles, involving a minor, active conformation and a major one which is not readily active. The formyl group would act as a specific trigger to select the active conformation. Experimental results are interpreted following this simple model and equilibrium parameters, together with kinetic constants of the peptidyltransferase activity, are presented.

Binding Sites↗