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M Jullien

Publications and source records attributed to M Jullien.

At least 37 records · Page 2Linked to original sources
PubMed1993

Crystal structure of a fluorescent derivative of RNase A.

The crystal structure of RNase A chemically modified with the fluorescent probe, N-[[(iodoacetyl)-amino]ethyl]-5-naphthylamine-1-sulfonic acid (1,5-IAENS), has been solved and refined to high resolution. It yields information on the mode of binding, the mobility of a probe commonly used in spectroscopic studies, and anion binding sites in RNase A. Trigonal crystals of the fluorescent derivative grown in sodium or cesium chloride and ammonium sulfate, pH 5.1, were nearly isomorphous with those of a semisynthetic RNase [DeMel, et al. (1992) J. Biol. Chem. 267, 247-256]. Refinement starting from semisynthetic RNase led to a model with R = 20% against 1.7-A diffraction data from crystals in ammonium sulfate and another model with R = 17% against 1.9-A data taken in the presence of 3 M NaCl. The second model contains three chloride ions: one is at the active site, and the other two are at molecular interfaces. Otherwise, the two models are very similar. The fluorophore has very little effect on the protein conformation. It is found to be covalently attached to the active site His-12 with the naphthyl group stacked on the imidazole ring of His-119. It remains largely accessible to solvent and in a polar environment on the protein surface, even though the fluorescence emission spectrum is blue shifted as it is in nonpolar solvents.

Amino Acid Sequence↗
PubMed1993

[Neural sarcoidosis in children. A case report].

A case of cerebral sarcoidosis of fortuitous discovery is reported in an adolescent. Neurosarcoidosis is exceedingly rare in the pediatric age groups. Clinical manifestations are widely variable and nonspecific, making diagnosis difficult in patients without extraneurologic involvement. The mainstay of management is early, prolonged corticosteroid therapy. Outcome varies with location of the lesions.

Adolescent↗
PubMed1992

Crystal packing in six crystal forms of pancreatic ribonuclease.

We compare the molecular packing of bovine pancreatic ribonuclease A (RNase A) in six crystal forms, two grown with alcohol, three with high salt and one with polyethylene glycol as a precipitant. The six packings differ in the number of molecules in contact and in the extent of the contacts, which bury 1570 A2 to 2790 A2 of the RNase surface. Regions of the protein surface involved in the six packings cover almost the whole RNase molecule. The abundance of polar interactions, about one per 200 A2, is the same in all types of precipitants. All molecule-to-molecule contacts are different in the six crystal forms, except for the one that forms a RNase dimer. The dimer has a large interface covering 1800 A2 and eight to ten polar interactions. Its presence in the three salt-grown crystal forms suggests that it is an intermediate in salt induced crystallization. In contrast, the two alcohol-grown forms contain only small interfaces, implying a different mechanism of nucleation.

Animals↗
PubMed1992

[Liddle syndrome (or pseudo-hyperaldosteronism). Long-term development and erythrocyte potassium flow study in 4 cases].

BACKGROUND: Liddle's syndrome (or pseudoprimary aldosteronism) is a rare hereditary disease; only 18 cases have been reported since 1963. Its cause remains unclear, but one of its features is increased cell membrane permeability to ions. PATIENTS AND METHODS: A diagnosis of Liddle's syndrome was made in 4 new cases, all female, two of them sisters (cases n0 3 and 4), at the ages of 2, 12, 5 and 4 years. The first manifestations were dehydratation with hypokalemia at 6 months (case n0 1), hypertension at 2 years (case n0 2), polydipsia with poor weight and height gain at 5 and 4 years of age (cases n0 3 and 4). At diagnosis, all the patients had severe hypertension, metabolic alkalosis, hypokalemia and hyperkaliuria, low plasma renin activity and serum aldosterone levels. Administration of antihypertensive agents was without effect, but the hypertension was reduced when triamterene and low-sodium diet were used. Hypercalciuria was observed in 2 cases and nephrocalcinosis in 2 (case n0 1 had both hypercalciuria and nephrocalcinosis). The 2 oldest patients (n0 3 and 4) developed progressive kidney failure, possibly due to reno-vascular disease secondary to hypertension. Patient n0 3 underwent kidney transplantation 18 years after the first symptoms of the disease. This resulted in the complete disappearance of her hypokalemia and hypertension. The red blood cell membrane permeability to K+ and Cl- was studied in all 4 cases before triamterene treatment. The passive permeability to K+ and (K+/Cl-) cotransport were both elevated. A second study, 3 years (cases n0 2 and 3) and 8 years (cases n0 1 and 4) later, of patients treated with triamterene showed low values for passive K+ permeability and (K+/Cl-)-cotransport. CONCLUSIONS: The 4 new cases of Liddle's syndrome had the classic features of the disease, except for hypercalciuria and nephrocalcinosis in 2 of them. The cell membrane permeability data are difficult to interpret. Hypokalemia and hypertension were immediately corrected after kidney transplantation in one case and remained so for 4 years, suggesting that this disease is tubular in origin.

Aldosterone↗
PubMed1990

Packing forces in ribonuclease crystals.

Packing in Ribonuclease A and Ribonuclease S crystals have been compared in order to determine the possible role of the precipitant on lattice contacts. Both proteins have similar tertiary structures, but they crystallize in different space groups depending on the precipitating agent. It is found that packing differs either by the number of nearest neighbours or by the size of surface areas buried in individual contacts. Ammonium sulfate seems to promote hydrophobic interactions with interfaces similar to those found in oligomeric proteins. Organic precipitants favour electrostatic interactions.

Amino Acids↗
PubMed1988

Allosteric transition of aspartokinase I-homoserine dehydrogenase I studied by time-resolved fluorescence.

The allosteric transition of threonine-sensitive aspartokinase I-homoserine dehydrogenase I from Escherichia coli has been studied by time-resolved fluorescence spectroscopy. Fluorescence decay can be resolved into 2 distinct classes of tryptophan emitters: a fast component, with a lifetime of about 1.5 ns; and a slow component, with a lifetime of about 4.5 ns. The fluorescence properties of the slow component are modified by the allosteric transition. In the T-form of the enzyme stabilized by threonine, the lifetime of the slow component is longer, with a red-shifted spectrum; its accessibility to quenching by acrylamide becomes slightly higher without any decrease of fluorescence anisotropy. These results indicate a change in polarity of the slow component environment. The quaternary structure change associated with the allosteric transition probably involves global movements of structural domains without leading to any local mobility on the nanosecond time-scale. We suggest that the slow component corresponds to the unique tryptophan of the buried kinase domain.

Acrylamide↗
PubMed1987

Early stimulation by EGF plus insulin of rRNA, c-fos, and actin mRNA expression: inhibition by cytochalasin D.

Stimulation of membrane ruffling is one of the first events induced by addition of growth factors to quiescent cultures. In order to assess the importance of intact cytoskeleton in induction, by EGF + insulin, of early events such as stimulation of rRNA, c-fos, and actin mRNA expression, we studied the effect of cytochalasin D (CD) on these metabolisms. We observed that CD slightly increased rRNA synthesis in nonstimulated cells; conversely, it decreased rRNA synthesis in cells stimulated by EGF + insulin. The maximal inhibition observed was 60%. The c-fos mRNA was not expressed in control cells and was accumulated in cells stimulated by the mixture of EGF + insulin; this accumulation was inhibited by CD. Actin mRNA was expressed in control cells and its expression was stimulated by EGF + insulin. Addition of CD decreased actin mRNA accumulation in stimulated cells but increased this accumulation in unstimulated cells. Our results, taken together, show that CD specifically affected the stimulation of rRNA and mRNA expression induced by growth factors and suggest that intact cytoskeleton and possibly membrane ruffling favored this stimulation.

Actins↗
PubMed1987

[Colonic necrosis, an unusual extrarenal involvement in hemolytic and uremic syndrome].

A seventeen years old girl presented a HUS. The usual gastrointestinal symptoms of the prodromal phase involved secondary complications leading to emergency surgical treatment. Laparotomy exploration revealed segmental necrosis of the colon which was treated by colectomy: histological studies revealed its ischemic nature with specific lesions of thrombotic microangiopathy. Later course was uneventful with the exception of renal failure requiring maintenance hemodialysis. Review of literature confirms the rare and severe nature of gastrointestinal lesions requiring surgery. Great care should be taken on one hand, not to undertake a useless operation and on the other hand to operate in time colonic necrosis involving or not intestinal perforation or intussusception.

Adolescent↗
PubMed1986

Quenching by acrylamide and temperature of a fluorescent probe attached to the active site of ribonuclease.

The fluorescence properties of ribonuclease labelled at its active site with N-(iodoacetylamino)-ethyl-5-naphthylamine-1-sulfonic acid have been studied at different temperatures and in the presence of acrylamide. The rate constant for the quenching of the fluorescence of labelled ribonuclease by acrylamide is apparently not limited by the "accessibility" of the probe: similar values are obtained for the native and denatured states of the protein. Instead, acrylamide seems to be a rather inefficient quencher of this fluorescent group [acetamidoamino)ethyl-5-naphthylamine-1-sulfonic acid), as shown by non-linear Stern-Volmer representations, biphasic decay kinetics, and a low value of the rate constant. The fluorescence intensity of the native state of the labelled protein is highly sensitive to temperature and exhibits a 20% decrease for an increase of temperature of from 10 degrees C to 30 degrees C, independent of solvent viscosity. This thermal quenching is specific for the native conformation and disappears when the protein is unfolded. When the fluorescence lifetime of the label is shortened by addition of acrylamide, the effect of temperature becomes identical for native and unfolded structures. This suggests that the cause of the thermal quenching is the presence of conformational fluctuations within the native protein which apparently take place in the time range from 35 to 200 ns.

Acrylamide↗
PubMed1984

Early release of the density-dependent inhibition of phosphate uptake and ATP synthesis after src gene expression in chick embryo fibroblasts.

Our results showed that the expression of the src gene in chick embryo fibroblasts (CEF) released the density-dependent inhibition (DDI) of phosphate metabolism (phosphate uptake and phosphorylation of small organic compounds). With increasing cell density, phosphate metabolism decreased by 58% in normal CEF and, in contrast, increased by 20% in Rous sarcoma virus (RSV)-transformed CEF. The same change in the DDI was observed in CEF infected by NY68 (a ts mutant for transformation of RSV) and maintained at the permissive temperature (37 degrees C) instead of the restrictive temperature (41.5 degrees C) for the expression of transformation. An interesting feature was that the release of the DDI of phosphate metabolism was an early event in the process of transformation, since it was almost concomitant with the stimulation of the pp60 src kinase activity following the shift from 41.5 to 37 degrees C of NY68 CEF. The phosphorylation of small organic compounds (Po) was more strongly increased by the change in temperature than was 32Pi accumulation. Furthermore, the percentage increases of Po and adenosine triphosphate (ATP) labelling with 32P were similar, suggesting that the expression of src gene enhanced ATP synthesis. In glucose-free medium, the stimulation of Po-labelling was still observed but was decreased. Therefore the activation of glycolytic activity is not an absolute requirement, but is necessary for the maximum effect of transformation on the release of DDI of phosphate metabolism. Oligomycin added in complete medium did not prevent the increase in Po-labelling. From these results, we assumed that ATP turnover was stimulated as a consequence of enhanced ATP degradation. We verified that the stimulation of Po phosphorylation was not a consequence of increased ATP utilization for RNA or protein synthesis. The stimulation of Po labelling was specifically abolished by quercetin. This drug inhibited the transformed cells more strongly than the non-transformed cells.

Adenosine Triphosphate↗
PubMed1984

Inhibition by quercetin of the release of density dependent-inhibition of cell growth in RSV-transformed chicken cells.

The expression of src gene in dense cultures of chick embryo fibroblasts (CEF) infected by a thermosensitive mutant (NY68) of RSV released density-dependent inhibition of growth and induced in these cells a large increase in DNA, RNA and protein synthesis. This stimulation of cellular metabolism was abolished in the presence of quercetin. Furthermore, quercetin added to the culture medium also inhibited the stimulation of pp60src kinase due to the expression of transformation.

Animals↗
PubMed1983

Energy-transfer measurements on a double fluorescent labeled ribonuclease A.

Two fluorescent groups have been covalently attached to ribonuclease A: first, the alpha-amino group is labeled upon reaction with fluorescein isothiocyanate, and second, one of the active site histidine residues is modified by N-[[(iodoacetyl)amino]ethyl]-5-naphthylamine-1-sulfonic acid. Among the products of these two successive chemical modifications, a derivative bearing one label on Lys-1 and the other label on His-119 can be isolated and characterized. Because of their spectral properties, these two fluorophores, fluorescein and N-[(acetamido)ethyl]-5-naphthylamine-1-sulfonic acid, are suitable for measuring resonance energy transfer within a single protein molecule. The efficiency of the energy transfer is close to 100% in the native state and is reduced to about 50% in the guanidine-unfolded state. This efficiency is further diminished upon reduction of the disulfide bonds in denaturing conditions. The efficiency of energy transfer has been determined independently from both emission and excitation spectra of the double-labeled protein, when unfolded with intact disulfide bonds. The average distance between the two fluorescent groups can be obtained from these measurements: it increases from 20 A at most in the native state to 46 A or more in the unfolded state.

Energy Transfer↗
PubMed1981

Fluorescent probe of ribonuclease A conformation.

The reaction of ribonuclease (RNase) with N-[[(iodoacetyl)amino]ethyl]-5-naphthylamine-1-sulfonic acid (1,5-IAENS) yields a derivative in which one fluorescent group is covalently attached to the protein. Several arguments suggest that the chemical modification has occurred at the enzyme active site: (i) 1,5-IAENS should have the same specificity as iodoacetamide, i.e., carboxymethylate one histidine of the active site; (ii) the derivatized protein is enzymatically inactive; (iii) in the native state of the protein, the fluorescent group is (almost) completely protected from the aqueous solvent; (iv) this group has no motions other than those of the protein. The fluorescence properties of the derivatized RNase change markedly upon unfolding induced by guanidine hydrochloride (Gdn . HCl), as seen from fluorescence intensity, maximum emission wavelength, and polarization measurements. Upon Gdn . HCl-induced unfolding, the fluorescent group is transferred from a nonpolar to a highly polar environment. Dynamic fluorescence measurements show also that unfolding results in a markedly increased mobility of the fluorescent label with respect to its proteic environment. These results are compared to those of Young & Potts (1963) [Young, D. M., & Potts, J. T. (1963) J. Biol. Chem. 238, 1995--2002], who studied the fluorescence properties of a surface-labeled derivative of RNase.

Endonucleases↗
PubMed1979

Amino Acid Uptake into Cultivated Mesophyll Cells from Asparagus officinalis L.

The uptake of threonine, aspartic acid, and isoleucine into cultivated asparagus cells was examined under culture conditions.Transport was linear with time and with the number of cells present in the assay. The upake of the three amino acids obeyed Michaelis-Menten kinetics with apparent affinities in the range of 0.1 to 0.02 millimolar. Azide and 2,4-dinitrophenol caused inhibition of threonine uptake. Reciprocal competitive inhibitions were found between threonine, aspartic acid, and isoleucine. Methionine and lysine competitively inhibited the uptake of these three amino acids. These results and the comparison of apparent affinities and inhibition constants are in favor of only one uptake system for threonine, aspartic acid, isoleucine, methionine, and lysine with different affinities for the different amino acids. All other amino acids with the exception of histidine, arginine, asparagine, and hydroxyproline inhibited threonine uptake. It is most likely that at least one component of the uptake system is shared by all amino acids.

Journal Article↗
PubMed1978

Dependence upon pH of steady-state parameters for the beta-galactosidase-catalysed hydrolyses of beta-D-galactopyranosyl derivatives of different chemical types.

The effect of pH upon the beta-galactosidase-catalyzed hydrolyses of aryl galactosides is essentially similar for each of the three steps of their hydrolysis. It differs markedly from that on the hydrolysis of galactosyl pyridinium salts; these proceed through a 'non-bottleneck' pathway. While pH increase abolishes the rate of every step of the reaction for aryl galactosides, it favors the first step of hydrolysis of the galactosyl pyridinium salts, which supports the hypothesis that catalysis of these compounds originates largely in non-covalent interactions.

Escherichia coli↗
PubMed1978

Diffusible factor(s) controlling density inhibition of 3T3 cell growth: a new approach.

In 3T3 Swiss mouse fibroblasts, incorporation of phosphate into cells and phosphorylation of small organic compounds were increased by shaking dense cultures. This response was not obtained with SV40 transformed Swiss 3T3 cells (SV-3T3). It appeared likely that these results could be accounted for by an inhibitor released from 3T3 cells but not from SV-3T3 cells. Our new method of co-incubation of sparse and dense cultures allowed us to demonstrate inhibition of growth and phosphate metabolism in sparse 3T3 cultures which were shaken in the presence of dense cultures. The inhibition was much less when the cultures were co-cultivated but not shaken. The inhibition of phosphate incorporation in acid-soluble and acid-insoluble fractions of sparse cultures was observed as early as 20 minutes of co-incubation in the presence of dense cultures, so this inhibition is not the result of depletion of growth factors in the medium. Our experiments suggest that an inhibitor(s) was released from dense cultures of 3T3 cells.

Cell Count↗