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M Morange

Publications and source records attributed to M Morange.

69 records · Page 4Linked to original sources
PubMed1977

Comparative study of the effect of 5' AMP and its analogs on rabbit glycogen phosphorylase b isoenzymes.

A comparative study of the effect of AMP and other nucleotides on the different rabbit glycogen phosphorylase b isoenzymes has been made: muscle, brain, liver isoenzymes, and the hybrid species between muscle and brain isoenzyme. We have studied either the direct kinetic effect of the different nucleotides or the action of the nucleotides on the b to a conversion rate. Muscle, brain, and muscle--brain isoenzymes are very strongly and very specifically activated by AMP and its analogs, whereas liver isoenzyme is not very sensitive to the nucleotides. However, muscle, brain and muscle--brain isoenzymes show slight but very interesting differences in their kinetic properties. These differences allow some speculations about the conformational state of these different isoenzymes.

Adenosine Monophosphate↗
PubMed1977

Conformations of purine ribosyl 5'-nucleotides bound to glycogen phosphorylase b. A proton T2 relaxation time investigation.

The conformation of 5'-nucleotides in the active site of glycogen phosphorylase b has been deduced from linewidth measurements of protons H-1', H-8 and H-2. It is shown by selective deuteration of the purine ring in position 8 that the orientation of the base is anti in the case of strong activators like AMP and syn in that of weak activators like IMP. The orientation correlation time of the nucleotides in the active site is nearly that of the enzyme, i.e. 160 ns at 21 degrees C.

Adenosine Monophosphate↗
PubMed1976

[A general method for the determination of the conformation of nucleotides bound to an enzyme site. Interaction between glycogen phsophorylase b and nucleoside-5'-monophosphates].

The conformation of 5' nucleotides in the active site of glycogen phosphorylase b has been deduced from T2 relaxation time of protons H1, H8 and H2. It is shown by deuterium substitution of the purine ring in position 8 that the orientation of the base is anti in the case of strong activators like adenosine 5'-monophosphate, and syn in that of weak activators like inosine 5'-monophosphate.

Adenosine Monophosphate↗
PubMed1976

AMP analogs: their function in the activation of glycogen phosphorylase b.

A series of AMP analogs has been selected in order to better understand the structural requirements (a) for the efficient binding of the activator molecule at the correct site on phosphorylase b from rabbit skeletal muscle and (b) for the activation which is observed. Two types of activation are known, according to Black and Wang [J. Biol. Chem. 243, 5892-5898 (1968)]: either a cooperative response with respect to the activator concentration (like the one which is obtained for AMP itself) or a non-cooperative response observed in the case of IMP. It is shown that the 5'-phosphate moiety is absolutely required for the analog to bind at the correct site (adenine or adenosine bind at another enzymic site), and that the free enthalpy, delta G, corresponding to the association process varies in a complex manner with respect to the substitution of the different positions of the AMP molecule. Moreover, the differences delta G (analog) - delta G (AMP) = delta G obtained for two types of substitution separately do not add up to the same energy difference as the one obtained when the two substitutions are made simultaneously on the AMP molecule. It appears that all the mononucleotides which have been tested up to now may be divided into two classes. Class I (AMP class) is characterized, apart from a strong activation, by the following features: (a) one molecule of analog expels two molecules of bound glucose 6-phosphate as it binds on the enzyme; (b) bound analog protects slowly one crucial cysteinyl residue against attack by 5,5'-dithio-bis(2-nitrobenzoic acid) at 4 degrees C; (c) association of two molecules of dimer is strengthened at 4 degrees C in the presence of the analog. Class II (IMP class) is associated with a weak activation and with the following set of properties: (a) a single molecule of bound glucose 6-phosphate is released as the first molecule of analog binds on the dimer; (b) two slowly reacting cysteinyl residues per subunit are immediately protected against 5,5'-dithio-bis(2-nitrobenzoic acid) by the binding of the analog at 4 degrees C; (c) the analog dissociates the low amount of tetramer which is present at 4 degrees C in the absence of AMP into two molecules of dimer. These results are discussed according to a plausible scheme of transconformations taking place in glycogen phosphorylase b, a model which has been derived earlier by relaxation studies.

Adenine↗
PubMed1976

A proton-relaxation-time study of the conformation of some purine and pyrimidine 5'-nucleotides in aqueous solution.

The measurement of proton relaxation time T1 in a series of purine and pyrimidine 5'-nucleotides has been carried out to investigate their conformation in dilute neutral aqueous solutions. The interpretation of relaxation data has been performed with the help of computer calculations taking into account the different conformers of the ribose ring and of the exocyclic group. It has been found that all nucleotides under study show nearly the same preferential orientations of the base defined by gamma0 = 70 degrees +/- 10 degrees in the syn range. A more elaborate treatment, using an angular distribution derived from calculated potentials on 5" -GMP gives theoretical relaxation times in close agreement with experimental ones.

Binding Sites↗
PubMed1976

1,N6-etheno-AMP and 1,N6-etheno-2'-deoxy-AMP as probes of the activator site of glycogen phosphorylase from rabbit skeletal muscle.

Both 1,N6-etheno-AMP and 1,N6-etheno-2'-deoxy-AMP bind at the AMP site of phosphorylase b (1,4-alpha-D-glucan:orthophosphate alpha-glucosyltransferase, EC 2.4.1.1). Etheno-AMP induces the same activation as AMP, about 30-fold higher than the activation induced by etheno-dAMP. The fluorescence of etheno-AMP and etheno-dAMP is associated with the base moiety; therefore, when free in solution, the two derivatives have identical fluorescence properties. However, when bound to phosphorylase, the fluorescence of etheno-AMP is quenched more efficiently than the fluorescence of etheno-dAMP. This difference between the fluorescence properties of the bound nucleotides suggests that a modification in the ribose ring affects the position of the adenine in the AMP site of phosphorylase b. The observed quenching may be due to a stacking interaction between an aromatic residue and the base moiety of the bound nucleotide.

Adenosine Monophosphate↗
PubMedDate not supplied

Differential heat-shock protein synthesis and response to stress in three avirulent and virulent Listeria species.

Two strains of Listeria monocytogenes, a virulent (V) and an avirulent (A) strain obtained by repeated in vitro cultivation at 37 degrees C, exhibited differing constitutive syntheses of heat-shock proteins (HSP) at 37 degrees C, the temperature of the infected host, and a differential response to heat treatment. These two strains also reacted differently to addition of a superoxide ion inducer and acid to treatments. Our observations were not limited to these two strains of L. monocytogenes: the level of HSP synthesis at 37 degrees C varied from one species of Listeria to another and was correlated with the thermo-inducibility of HSP. In an accompanying paper, we will attempt to establish whether these different biosynthetic properties observed in vitro between A and V L. monocytogenes enable the prediction of their properties/survival once inside the resident peritoneal murine macrophages.

Bacterial Proteins↗
PubMedDate not supplied

Absence of an early detectable increase in heat-shock protein synthesis by Listeria monocytogenes within mouse mononuclear phagocytes.

We investigated the behaviour of Listeria monocytogenes during the early phase of its in vitro phagocytosis by mouse resident peritoneal macrophages, and compared behaviour and modifications in protein synthesis occurring in a virulent and a non-virulent strain of L. monocytogenes. As previously shown, these two strains have differential responses to stress and heat shock in vitro. At between 1 and 3 h of phagocytosis, there is a general decrease in protein synthesis in Listeria. Synthesis of the major DnaK and GroEL heat-shock proteins also decreases. Synthesis of only a limited set of bacterial proteins is conserved or even increased during this early phase of phagocytosis. Similar modifications in protein synthesis are also observed in bacteria which have had only transient contact with macrophages without being phagocytosed. The discrimination, by the macrophage, between non-virulent and virulent L. monocytogenes occurs less than 30 min after initiation of phagocytosis: avirulent Listeria are totally degraded inside the resident peritoneal macrophages, whereas a significant fraction of virulent Listeria remain undamaged and alive. The distinct behaviour of the two strains of Listeria thus appears to be independent of a drastic change in bacterial protein biosynthesis.

Animals↗
PubMedDate not supplied

Heat shock proteins, first major products of zygotic gene activity in mouse embryo.

In many species, the early post-fertilization development of the egg appears to occur mainly under maternal control and does not require transcription of the embryonic genome. In the mouse this situation is restricted to the one-cell stage; activation of the embryonic genome occurs at the late two-cell stage and results in a drastic change in the spectrum of proteins synthesized. This activation is preceded by a decrease in the overall synthesis of proteins at the end of the one-cell stage and the appearance, at the early two-cell stage, of a set of new polypeptides of molecular weight approximately 70,000 (70K) (refs 2, 8, 9). This can be compared with the series of events that occur after hyperthermia in differentiated cells. Heat shock results in an arrest of most transcription and translation; subsequently, expression of a limited set of genes, the heat shock genes, precedes the overall reactivation of cellular genome. Here we show that the 70K early two-cell-specific proteins are identical to two of the mouse heat shock proteins, HSP 68 and HSP 70.

Animals↗
PubMedDate not supplied

Phenotypic characterization of mouse embryonic fibroblasts lacking heat shock factor 2.

In murine cells, the heat shock response is regulated by a transcription factor, HSF1, which triggers the transcription of heat shock genes. HSF2 has been shown to be involved in meiosis and mouse brain development. We characterized the effects of the absence of HSF2 in mouse embryonic fibroblasts (MEFs). The temperature threshold of the heat shock response appeared lowered in Hsf2(-/-) MEFS as monitored by the synthesis of heat shock protein HSP70. In contrast to unstressed wild type MEFS, HSP70 and HSF1 are localized in the nucleus of unstressed Hsf2(-/-) MEFS, a characteristic of stressed cells. HSF1 is not activated for DNA-binding at unstressed temperature in Hsf2(-/-) MEFS. Therefore, the absence of HSF2 induces some but not all of the characteristics of the stress response. In addition, Hsf2(-/-) MEFS exhibited proliferation defects, altered morphology, remodeling of the fibronectin network.

Actins↗