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R Brasseur

Publications and source records attributed to R Brasseur.

At least 163 records · Page 9Linked to original sources
PubMed1987

Expression at the cell surface of native fusion protein of the Newcastle disease virus (NDV) strain Italien from cloned cDNA.

A cDNA library was constructed with poly(A)+-mRNAs from NDV-Italien infected BHK-21 cells. A clone, that hybridized to the F gene mRNA, was sequenced. A long open reading frame encodes for a protein of 553 amino acids, with a calculated molecular weight of 59,153, consisting of twelve cysteine residues and six potential glycosylation sites. The protein sequence contains a hydrophobic region at the N-terminus of F1 and a presumptive long transmembrane fragment near the C-terminus. Comparison of the F proteins from NDV strains Italien and Australia-Victoria shows that the sequences are very similar, with conservation of most cysteine residues and of the potential glycosylation sites. The F coding sequence was inserted into the genome of vaccinia virus under the control of vaccinia P7.5 transcriptional regulatory sequences. Expression of F protein was demonstrated by indirect immunofluorescence with five anti-F monoclonal antibodies known to react with conformational epitopes.

Amino Acid Sequence↗
PubMed1986

Mechanism of inhibition of mitochondrial enzymatic complex I-III by adriamycin derivatives.

We demonstrate here that complex I-III of bovine heart mitochondrial membrane is inhibited by adriamycin derivatives. This inhibition is a cardiolipin-dependent process. This lipid, specific to the inner mitochondrial membrane, has been shown previously to interact specifically with adriamycin in model membranes (Goormaghtigh, E., Chatelain, P., Caspers, J. and Ruysschaert, J.-M. (1980) Biochim. Biophys. Acta 597, 1-14) and in mitochondrial membranes (Cheneval, D., Müller, M., Toni, R., Ruetz, S. and Carafoli, E. (1985) J. Biol. Chem. 260, 13003-13007). The differential scanning calorimetry data indicate that, in multilamellar liposomes, the formation of antibiotic-cardiolipin complexes induces a clustering of cardiolipin molecules. Conformational analysis of the antibiotic-cardiolipin complexes suggests that plane-plane interactions between the antibiotics aromatic moieties stabilize this complex formation. Possible mechanisms of inactivation of complex I-III by adriamycin are proposed.

Animals↗
PubMed1986

pH dependent insertion of a diphtheria toxin B fragment peptide into the lipid membrane: a conformational analysis.

A peptide of diphtheria toxin B fragment (residues 147-266) has been shown to induce pore formation in lipid bilayer membranes at low pH. Such an effect was obtained at a much lower extent or not at all at pH = 7. The region localized between residues 225 and 246 is highly hydrophobic (27.3% polarity) and characterized by a high concentration of proline residues. Since proline cis-trans isomerization is highly sensitive to the pH of the medium, we investigated the capability of the cis and trans isomers to penetrate into the lipid matrix. Obviously, the cis-trans isomerization of proline 242 and 245, assumed to be imposed by a low pH, uncovers the hydrophobic region and induces its insertion into a lipid layer of dipalmitoylphosphatidylcholine. The lipid matrix destabilization resulting from this process could promote the penetration into the lipid bilayer of an amphipatic structure (153-178) similar to the transverse lipid associating domains of membrane proteins.

Diphtheria Toxin↗
PubMed1986

Protonophoretic activity of hypoglycemic sulfonylureas in black lipid membranes.

The ability of glibenclamide and of gliclazide to act as protonophores has been studied in black lipid membranes made of glycerol monoleate as a function of pH and drug concentration. Protons may effectively be transported across lipid membranes with a maximum at a pH close to the pKa of the sulfamide (pKa of glibenclamide = 5.4). It is suggested therefore that hypoglycemic sulfonylureas may act in part as Ca2+ inward and H+ outward ionophores through plasma membranes of pancreatic B cells.

Biological Transport↗
PubMed1986

Use of hydrophobicity profiles to predict receptor binding domains on apolipoprotein E and the low density lipoprotein apolipoprotein B-E receptor.

We have used mean hydrophobicity and hydrophobic moment calculations to predict the receptor binding domains in apolipoprotein E and in the low density lipoprotein apolipoprotein B-E receptor. In apolipoprotein E, two receptor binding domains, residues 136-160 and 214-236, having a high hydrophilicity and a high mean helical hydrophobic moment, were identified. The first domain has been located experimentally and mutations influencing the hydrophobicity parameters of the binding site have been shown to affect the receptor binding. The second domain is probably, either separately or in combination with the first domain, involved in receptor binding or in heparin binding. In the low density lipoprotein apolipoprotein B-E receptor, six protein domains were identified. In the first domain (residues 1-371), eight hydrophilic maxima, organized in pairs through disulfide bonds, form the four experimentally observed receptor binding sites. These sites consist of repeats of 26 amino acids but differ from those reported by others [Yamamoto, T., Davis, C. G., Brown, M. S., Schneider, W. J., Casey, M. L., Goldstein, J. W. & Russell, D. W. (1984) Cell 39, 27-38]. The second, more hydrophobic, domain (residues 372-640) forms the core of the receptor, explaining its homology with the precursor of mouse epidermal growth factor, while the cysteine residues in the third domain (residues 641-699), interacting with those of the first domain, further stabilize the molecule. Beyond the fourth hydrophilic domain (residues 700-767), to which carbohydrates are linked, a very hydrophobic membrane spanning region (residues 768-789) could be detected easily. The last domain (residues 790-839), situated in the cytoplasma, contains hydrophilic maxima, as this region might interact with clathrin-related proteins. These data suggest that hydrophobicity analysis can detect and predict protein domains: hydrophilic receptor sites as well as hydrophobic core-forming and membrane-spanning regions.

Amino Acid Sequence↗
PubMed1986

Properties of amiodarone monolayer spread at the air-water interface.

Surface pressure measurements demonstrate that, over a wide range of pH, amiodarone forms a stable monolayer at the air-water interface. The area found to be occupied by an amiodarone molecule was compared with a theoretical prediction based on a conformational analysis, making it possible to assemble amphiphilic molecules. The intrinsic ionization constant of amiodarone in an aqueous environment pKi = 8.7 +/- 0.5 was evaluated from surface potential measurements.

Air↗
PubMed1986

Divergent calciphoretic properties of negatively charged phospholipids in a two-phase system and in liposomes.

The ionophoretic properties of several negatively charged phospholipids for transporting calcium ions in an organic phase and across membranes of lipid vesicles have been studied. The amounts of Ca2+ translocated in the organic phase depend on the lipid type but also on the nature of the hydrocarbon chains. Under our experimental conditions, Ca2+ outflow from liposomes is observable with phosphatidic acid derived from egg yolk (PA) and with bovine brain phosphatidyl serine (PS) while dipalmitoyl phosphatidic acid (DPPA), cardiolipin (CL), phosphatidyl inositol (PI) and phosphatidyl inositol diphosphate (PIP2) remained unactive as calcium ionophores through lipid membranes but active as calcium translocators in an organic phase.

Animals↗
PubMed1985

Structural considerations for calcium ionophoresis by prostaglandins.

The prostaglandins PGB2, PGE2 and PGF2 alpha were found to translocate calcium in a modified Pressman cell. At pH 7.40, PGB2 was more potent than PGE2 and than PGF2 alpha. When incorporated at a 1% molar ratio in liposomes made of cholesterol and different diacyl phosphatidyl choline, prostaglandins are able to mediate a slow calcium exchange diffusion. A significant prostaglandin-mediated calcium release that depends on the lipid matrix rigidity is observable at 37 degrees but not at 22 degrees. Conformational analysis of the complex formed by two molecules of prostaglandins and one calcium atom, either at a simulated membrane-water interface or in a simulated bulk lipid phase reveals rigid complexes with great distances between hydrophilic and hydrophobic gravity centres that predict low ionophoretic properties.

Calcium↗
PubMed1985

Semi-empirical conformational analysis of propranolol interacting with dipalmitoylphosphatidylcholine.

A semi-empirical conformational analysis is used to compute the conformation of (+)-propranolol inserted in dipalmitoylphosphatidylcholine. In a first step, the minimal conformational energy of the isolated molecule at the hydrocarbon-water interface is calculated as the sum of the contributions resulting from the Van der Waals, the torsional, the electrostatic and the transfer energies. Five pairs of conformers of minimal energy are determined. They are compared to data available from other experimental approaches. In a second step, they are assembled with dipalmitoylphosphatidylcholine at the interface. Although propranolol is considered in its protonated form, the electrostatic interaction with dipalmitoylphosphatidylcholine is negligible as compared to the Van der Waals interaction. The area occupied per propranolol molecule is between 0.53 and 0.64 nm2/molecule. In the most probable modes of insertion of propranolol into the lipid layer, the naphthyl moiety of the compound interacts with the lipid acyl chains. The protonated amino group is located in the vicinity of the phosphate residue possibly causing an electrostatic interaction.

Chemical Phenomena↗
PubMed1985

Interaction of streptomycin and streptomycylamine derivatives with negatively charged lipid layers. Correlation between binding, conformation of complexes and inhibition of lysosomal phospholipase activities.

Aminoglycoside antibiotics induce a lysosomal phospholipidosis in kidney proximal tubules after conventional therapy in animals and man. We have previously demonstrated that these drugs bind to negatively charged phospholipid bilayers at acid pH and inhibit the activity of lysosomal acid phospholipases in vitro and in vivo. A combined biochemical and conformational study [Brasseur et al., Biochem. Pharmac. 33, 629 (1984)] showed major and consistent differences between 6 aminoglycosides in current clinical use with respect to the stability of the complexes they form with phosphatidylinositol, their inhibitory potency towards the activity of lysosomal phospholipases and their current toxicity ranking (e.g. gentamicin greater than amikacin greater than streptomycin). In the present study we have extended this approach to experimental derivatives of streptomycin. The derivatives examined were: dihydrostreptomycin, dideguanyldihydrostreptomycin, streptomycylamine, dideguanylstreptomycylamine, N-butyl- and N-benzyl-dideguanylstreptomycylamine. These compounds were examined for (i) their binding to negatively charged liposomes, measured by gel permeation on Sepharose 4B; (ii) their interactions with phosphatidylinositol assessed by semi-empirical conformational analysis and (iii) their inhibitory effect on the activities of lysosomal phospholipases towards phosphatidylcholine present in negatively charged liposomes. Streptomycin and gentamicin were also used as reference compounds with low and high affinity (and inhibitory potency), respectively. Our observations can be summarized as follows: (i) the replacement of the aldehyde in the streptose ring by a methylamino group strikingly changes the conformation of the molecule, allowing a better interaction with phosphatidylinositol. Thus, streptomycylamine binds much more tightly to phospholipid bilayers and shows a higher inhibitory potency towards phospholipase activity, as compared to streptomycin. The conformational analysis shows, however, that this effect is only partially due to the additional cationic charge carried by streptomycylamine. Other modifications of the streptomycin molecule, such as the replacement of the guanidinium groups by aminogroups or the addition of hydrophobic moieties (butyl or benzyl groups) to the streptose do not markedly further strengthen the interactions of the molecule with phosphatidylinositol. (ii) Even though some derivatives (e.g. dideguanylstreptomycylamine) bind as tightly to phospholipids as gentamicin, they remain much less inhibitory towards lysosomal phospholipases.(ABSTRACT TRUNCATED AT 400 WORDS)

Aminoglycosides↗
PubMed1985

Structural analogies between protein kinase C activators.

Phorbol esters and diacylglycerols activate protein kinase C but specific structural parameters appear to be required for the enzyme activation. We have analyzed the conformation of potent and not potent diacylglycerols and phorbol esters. The orientation of the CH20H group at C3 of 1,2 diolein is remarkably similar to that of the same group at C-20 of 4 beta phorbol didecanoate and crucial for potency in activating the enzyme. Our data suggest that the new conformational approach here described could be used to rationally design specific inhibitors preventing the effects of tumor promoters and to predict the structure of potential tumor promoters.

Acetylation↗
PubMed1985

Hydrolysis of phosphatidylcholine liposomes by lysosomal phospholipase A is maximal at the phase transition temperature of the lipid substrate.

We have measured the rate of hydrolysis of liposomes made of DL-alpha-dipalmitoylphosphatidylcholine (DPPC) and L-alpha-dimyristoylphosphatidylcholine by a soluble fraction of highly purified lysosomes isolated from rat liver. Phospholipids are hydrolyzed into lysophospholipids and fatty acids at a rate which is maximal near the temperature characteristic of the gel to liquid crystalline phase transition of the lipid bilayer. This strong influence of the physical properties of the substrate on the enzyme activity suggests a structural analogy between the lysosomal phospholipases of the A type (EC 3.1.1.32 and EC 3.1.1.4) and the pancreatic phospholipase A2.

Animals↗
PubMed1984

Evolution of the thermotropic properties of large unilamellar vesicles (LUV).

The evolution of the thermotropic properties of large unilamellar vesicles (LUV) made by the reverse-phase evaporation technique has been studied by differential scanning calorimetry (DSC) and by fluorescence polarization of the diphenylhexatriene probe inserted in the lipid phase. Lipid fluidity and transition temperatures of DL-alpha-dimyristoyl-and DL-alpha-dipalmitoyl-phosphatidylcholine vesicles were practically not modified at room temperature (19-20 degrees C), even after several days. Because a better knowledge of the physico-chemical properties of LUV seems essential for its use as a model membrane or as a carrier of exogenous material into cells, we compare it with the stability of the widely used multilamellar (MLV) and sonicated unilamellar vesicles (SUV).

Calorimetry↗
PubMed1984

Conformational analysis of suloctidil and derivatives inserted in lipid layers.

Interaction between suloctidil (CP 556 S) and lipids (phosphatidylcholine, phosphatidylserine) is studied using a new conformational analysis procedure. This analysis is extended to two compounds related to suloctidil but bearing no protonable group (CP 894 S) or of different hydrophobicity (CP 1136 S). It gives a molecular description of the mode of insertion of the drugs into the lipid layer. The influence of the calculated lipid-drug interaction and area occupied per drug molecule in the lipid layer is tentatively related to the effect on the lipid dynamics. For a given conformer, an effect on the lipid dynamics is expected only if (a) the area occupied per conformer is similar to that of the lipid and/or (b) the drug-lipid interaction energy is equal or superior to that of the lipid-lipid interaction. These predictions are analyzed in terms of the available experimental data.

Lipids↗
PubMed1984

Interactions of aminoglycoside antibiotics with negatively charged lipid layers. Biochemical and conformational studies.

Previous studies [Laurent et al., Biochem. Pharmac. 31, 3861 (1982)] have demonstrated that aminoglycoside antibiotics bind to negatively charged phospholipid bilayers and inhibit the activity of lysosomal phospholipases. This inhibition also occurs in vivo in animal and man. It is considered to be an early and significant step in the development of aminoglycoside-induced nephrotoxicity. The binding of 6 aminoglycosides in current clinical use (dibekacin, gentamicin, tobramycin, kanamycin A, amikacin and streptomycin) to phosphatidylinositol has been studied by gel filtration technique and by conformational analysis. Variation of the phosphatidylinositol content from 0 to 27% of total phospholipids causes a cooperative increase in aminoglycoside binding. At fixed phosphatidylinositol concentration, the binding of the different aminoglycosides is related to the number of aminogroups carried by the drug (viz., gentamicin greater than kanamycin A greater than streptomycin) and is largely, but not entirely dependent upon electrostatic interactions. Conformational analysis of the interaction of aminoglycosides with phosphatidylinositol monolayers was made by a step-wise computation approach. We first have taken into account the Vander Waals, torsional and electrostatic energies and we have calculated the hydrophobic and hydrophilic centers of each molecule. Assembly was then computed by successive association of one molecule of drug and up to 4 molecules of phosphatidylinositol. The calculated interaction energies varied from -8.5 kcal/mol (gentamicin) to -4.9 kcal/mol (amikacin) and -3.9 kcal/mol (streptomycin).(ABSTRACT TRUNCATED AT 250 WORDS)

Aminoglycosides↗