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B Guerin

Publications and source records attributed to B Guerin.

At least 37 records · Page 2Linked to original sources
PubMed1989

The role of subunit 4, a nuclear-encoded protein of the F0 sector of yeast mitochondrial ATP synthase, in the assembly of the whole complex.

The yeast nuclear gene ATP4, encoding the ATP synthase subunit 4, was disrupted by insertion into the middle of it the selective marker URA3. Transformation of the Saccharomyces cerevisiae strain D273-10B/A/U produced a mutant unable to grow on glycerol medium. The ATP4 gene is unique since subunit 4 was not present in mutant mitochondria; the hypothetical truncated subunit 4 was never detected. ATPase was rendered oligomycin-insensitive and the F1 sector of this mutant appeared loosely bound to the membrane. Analysis of mitochondrially translated hydrophobic subunits of F0 revealed that subunits 8 and 9 were present, unlike subunit 6. This indicated a structural relationship between subunits 4 and 6 during biogenesis of F0. It therefore appears that subunit 4 (also called subunit b in beef heart and Escherichia coli ATP synthases) plays at least a structural role in the assembly of the whole complex. Disruption of the ATP4 gene also had a dramatic effect on the assembly of other mitochondrial complexes. Thus, the cytochrome oxidase activity of the mutant strain was about five times lower than that of the wild type. In addition, a high percentage of spontaneous rho- mutants was detected.

Adenosine Triphosphatases↗
PubMed1989

Thermodynamic and kinetic control of ATP synthesis in yeast mitochondria: role of delta pH.

ATP synthesis rate, measured as the variation in external Pi concentration, varied as a linear function of either delta mu H+ or delta Gpin, in such a manner that the delta Gpin/delta mu H+ ratio increased while VATP increased. We also observed a linear dependence of the flux control coefficient of the Pi carrier on delta pH. All the results presented can be explained by a relatively large delta pH drop when VATP increases.

Adenosine Diphosphate↗
PubMed1989

The yeast ATP synthase subunit 4: structure and function.

The structure of ATP synthase subunit 4 was determined by using the oligonucleotide probe procedure. This subunit is the fourth polypeptide of the complex when classifying subunits in order of decreasing molecular mass. Its relative molecular mass is 25 kDa. The ATP4 gene was isolated and sequenced. The nucleotide sequence predicts that subunit 4 is probably derived from a precursor protein 244 amino acids long. Mature subunit 4 contains 209 amino acid residues and the predicted molecular mass is 23250 kDa. Subunit 4 shows homology with the b-subunit of Escherichia coli ATP synthase and the b-subunit of beef heart mitochondrial ATP synthase. By using homologous transformation, a mutant lacking wild subunit 4 was constructed. This mutant is devoid of oxidative phosphorylation and F1 is loosely bound to the membrane. Our data are in favor of a structural relationship between subunit 4 and the mitochondrially-translated subunit 6 during biogenesis of F0.

Amino Acid Sequence↗
PubMed1988

Localization of the synthesis of very-long-chain fatty acid in mitochondria from Saccharomyces cerevisiae.

The localization of the mitochondrial elongation activities ('elongases') from Saccharomyces cerevisiae has been investigated. It was shown, using carboxyatractyloside in the incubation mixture, that synthesis of very-long-chain fatty acids probably occurred outside the matrix and, by fractionation experiments, that elongases are membrane-bound enzymes. The solubilization of the outer membrane by digitonin showed that three elongating activities are correlated with a marker of the outer membrane and not with an inner membrane marker. A further partial purification of the outer membrane showed that elongases are present in the outer membrane of mitochondria.

Acyl-Carrier Protein S-Malonyltransferase↗
PubMed1988

Redistribution of the flux-control coefficients in mitochondrial oxidative phosphorylations in the course of brain edema.

This work describes the control exerted by dicarboxylate carrier and succinate dehydrogenase activities on the oxidative phosphorylations in rabbit brain mitochondria as an edema develops. Vasogenic edema leads to an uncompetitive inhibition of succinate dehydrogenase activity and to a large decrease of oxidative phosphorylations linked to succinate utilisation. Naftidrofuryl treatment in vivo restores both a high succinate dehydrogenase activity and a normal respiratory rate. In order to quantify the control of oxidative phosphorylations by the succinate dehydrogenase step, we applied the control analysis (Kacser, H. and Burns, J.A. (1973) in Rate Control of Biological Processes (Davies, D.D., ed.), pp. 65-104, Cambridge University Press, London; Heinrich, R. and Rapoport, T.A. (1974) Eur. J. Biochem. 42, 89-95). By using two inhibitors, one (phenylsuccinate) acting only on the dicarboxylate carrier and another (malonate) acting on both the dicarboxylate carrier and the succinate dehydrogenase, a method was developed to calculate the control coefficients of these two steps. The main result is that in mitochondria isolated from normal tissue succinate dehydrogenase exerted no control, but in the course of edema this enzymatic step became a controlling one: a transition from zero to a high control coefficient (0.5) was observed from the onset of intracellular edema for the threshold value of water/dry-weight tissue of 4.6.

Animals↗
PubMed1988

Comparative studies on the glycolytic and hexose monophosphate pathways in Candida parapsilosis and Saccharomyces cerevisiae.

Some enzymatic activities of the glycolytic and hexose monophosphate pathways of Candida parapsilosis, a yeast lacking alcohol dehydrogenase but able to grow on high glucose concentrations, were compared to those of Saccharomyces cerevisiae. Cells were grown either on 8% glucose or on 2% glycerol and activities measured under optimal conditions. Results were as follows: glycolytic enzymes of C. parapsilosis, except glyceraldehyde 3-phosphate dehydrogenase, exhibited an activity weaker than that of S. cerevisiae, especially when yeasts were grown on glycerol. Fructose-1,6 bisphosphatase, an enzyme implicated in gluconeogenesis and in the hexose monophosphate pathway, and known to be very sensitive to catabolite repression in S. cerevisiae, was always active in C. parapsilosis even when cells were grown on 8% glucose. However, the allosteric properties towards AMP and fructose-2,6-bisphosphate were the same in both strains. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, two other enzymes of the hexose monophosphate pathway, exhibited a higher activity in C. parapsilosis than in S. cerevisiae. Regulation of two important control points of the glycolytic flux, phosphofructokinase and pyruvate kinase, was investigated. In C. parapsilosis phosphofructokinase was poorly sensitive to ATP but fructose-2,6-bisphosphate completely relieved the light ATP inhibition. Pyruvate kinase did not require fructose-1,6-bisphosphate for its activity, and by this way, did not regulate the glycolytic flux.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1988

Skin tests.

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Allergens↗
PubMed1987

Modification of flow-force relationships by external ATP in yeast mitochondria.

The purpose of this work is to measure protonmotive force and cytochrome reduction level under different respiratory steady states in isolated yeast mitochondria. The rate of respiration was varied by using three sets of conditions: (a) different external phosphate concentrations with a fixed concentration of ADP (ATP synthesis) and (b) different concentrations of carbonylcyanide m-chlorophenylhydrazone in the presence of oligomycin and carboxyatractylate (uncoupling) either in the absence or (c) in the presence of external ATP. ADP plus phosphate stimulates respiration more than uncoupler at the same protonmotive force value. However, the relationships between respiratory rate and protonmotive force were similar when stimulation was induced either by ADP + Pi or by carbonylcyanide m-chlorophenylhydrazone in the presence of ATP. At the same respiratory rate, cytochrome a + a3 is more reduced by uncoupler than by ADP + Pi additions. However, the relationships between respiratory rate and reduction level of cytochrome-c oxidase are similar both under ATP synthesis and with uncoupling conditions in the presence of external ATP. Control of respiration exerted by cytochrome-c oxidase, and support the view the condition mentioned above. This control was low when the respiratory rate was varied by the ATP synthesis rate; it increased as a function of the respiratory rate with uncoupler in the absence of ATP. ATP decreased this control under uncoupling conditions. These results suggest a regulatory effect of external ATP on cytochrome-c oxidase, and support the view that the relationships between respiratory rate and protonmotive force, on the one hand, and respiratory rate and the reduction level of cytochrome-c oxidase, on the other, depend respectively on the kinetic regulations of the system.

Adenosine Triphosphate↗
PubMed1987

Fatty acid synthesis in mitochondria from Saccharomyces cerevisiae.

The ability of purified mitochondria isolated from S. cerevisiae to synthesize fatty acids and especially very long chain fatty acids (VLCFA) has been investigated. The VLCFA synthesis requires malonyl-CoA as the C2 unit donor and NADPH as the reducing agent. Moreover the yeast mitochondrial elongase is able to accept either exogenous long chain fatty acyl-CoAs as substrates or elongate endogenous substrates. In the latter case, ATP is required for full activity. Besides this important VLCFA formation, the mitochondria from S. cerevisiae were also able to synthesize C16 and C18.

Acetyltransferases↗
PubMed1986

Localisation of the hydrophilic C terminal part of the ATP synthase subunit 8 of Saccharomyces cerevisiae.

The hydrophobic subunit 8 of the yeast ATP synthase was modified using the non-penetrating amino reactive specific reagent: isethionylacetimidate. The polypeptide was modified when using the isolated ATP synthase and sodium bromide-treated submitochondrial particles. It is shown that the only lysine of the protein was modified by the reagent. It is concluded that the hydrophilic C terminal part of the protein containing lysine 47 is located on the inner side of the inner mitochondrial membrane.

Amino Acid Sequence↗
PubMed1986

[Allergy to domestic and laboratory animals].

Animal proteins originating from numerous tissues whose epithelial debris represent very powerful allergens and sensitize numerous patients. Sensitization may occur very early, appearing while suckling. From the time this allergy is acquired to animal proteins, it may persist lifelong even in the absence of further contact. Recent knowledge in immunochemistry has enabled greater precision in the allergic origin of these disorders and to quantify them both in the domestic and industrial environment. Among the animals most prone to produce allergies, the cat and rodents have a particular importance. The improvement in the qualitative assessment of animal allergens allows a more precise diagnosis and when eviction is impossible the treatment of certain patients by desensitization. In allergies in laboratory animals the most powerful allergens are found in urine. Male animals are more allergenic than females. Effective preventative measures are currently under study but seem to allow a diminution in the frequency of sensitization and the seriousness of allergic manifestations. Finally the most recent aspect concerns cross reactivity between animals. This explains how certain individuals who have never been in contact with an animal of a particular species may experience an allergic reaction on the first contact.

Allergens↗
PubMed1986

Specific IgE response before and after rush immunotherapy with a standardized allergen or allergoid in grass pollen allergy.

Allergen extracts contain a wide variety of allergenic determinants and the sensitization of allergic subjects is extremely heterogeneous. Specific immunotherapy is usually performed with multiple component extracts and it is therefore important to determine whether this treatment may elicit the onset of newly developed IgE sensitivities. By means of nitrocellulose immunoblotting technique, the IgE sensitivities of 20 patients were characterized before and after specific immunotherapy. Ten patients had a rush immunotherapy with a standardized orchard grass pollen extract and ten others underwent a rush immunotherapy with a 6-grass pollen allergoid. The allergenic profiles of the patients before and after immunotherapy were qualitatively similar. In some patients an increase of orchard grass pollen-specific IgE was observed and the allergenic profile was quantitatively different. These results suggest that rush immunotherapy with either an aqueous non-modified extract or an allergoid does not elicit the onset of new IgE sensitivities. Multicomponent allergenic extracts may therefore be used in the treatment of patients.

Adolescent↗
PubMed1986

[Approach to effects on health of hydro-agricultural development in tropical regions. Calculation of absenteeism].

A method is proposed for comparing the number of lost work days for a rural population in a tropical area. It takes into account the pathology of the whole population and not only of the working people. It uses demographic, epidemiologic and clinical data which are generally available. This method allows to assess the usefulness of health programs with regard to the increase of productivity. The example of Mali is presented.

Absenteeism↗
PubMed1985

Substrate-level phosphorylation in isolated yeast mitochondria.

The activity and the control of substrate-level phosphorylations in isolated yeast mitochondria were investigated. The oligomycin-insensitive ATP synthesis rate linked to 2-oxoglutarate oxidation is of similar order of magnitude to that observed in oxidative phosphorylation. The flux control coefficients of respiratory chain activity, translocase and phosphate carrier activities were close to zero. Kinetic control was confined to 2-oxoglutarate supply and 2-oxoglutarate dehydrogenase complex activity. The study of endogenous nucleotide phosphorylation showed that ADP is the first phosphate acceptor during this process. Moreover, the comparison between the whole intramitochondrial content of nucleotides and phosphate to the fraction involved in substrate-level phosphorylation indicated a metabolic compartmentation of nucleotides and phosphate. A linear relationship was observed between the 2-oxoglutarate-linked ATP synthesis rate and the internal phosphate potential: delta G'p = delta G'o + RT 1n ([ATP]/[ADP] [Pi]). The fact that the substrate-level phosphorylation process alone was able to maintain a high internal phosphate potential has an important bioenergetic consequence, particularly for yeast grown on fermentable substrates.

Adenosine Diphosphate↗