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F Payan

Publications and source records attributed to F Payan.

34 records · Page 2Linked to original sources
PubMed1993

Intramolecular electron transfer in ferredoxin II from Desulfovibrio desulfuricans Norway.

In order to elucidate the role of the two (4Fe-4S) clusters in ferredoxins and to determine whether an electron-transfer mechanism may occur between the clusters, the in vitro reduction of cytochrome c3 and cytochrome c553 by Desulfovibrio desulfuricans Norway ferredoxin II was studied using spectrophotometric techniques. Ferredoxin II, covalently cross-linked with either cytochrome c3 or c553, is an obligate intermediate in cytochrome reduction by pyruvate dehydrogenase. Both titration of the complex formation under 1H-NMR spectroscopy and cross-linking experiments between ferredoxin II and either cytochrome c3 or cytochrome c553 gave a stoichiometric ratio of 1:1. Modelling the protein yielded differences between the charge distributions around the two (Fe-S) clusters. The fact that Cluster 2 is blocked in the electron-transfer domain facing the cytochrome interacting heme, indicates Cluster 1 receives electron from pyruvate dehydrogenase. Consecutively, cytochrome reduction occurs owing to an intramolecular electron exchange between the two clusters of the ferredoxin. The properties of two (Fe-S) cluster ferredoxins are compared to those of monocluster ferredoxins and discussed in evolutionary terms.

Amino Acid Sequence↗
PubMed1993

Structure and molecular model refinement of pig pancreatic alpha-amylase at 2.1 A resolution.

The previously reported structural model of porcine pancreatic alpha-amylase has been corrected and improved by a genuinely independent structure solution. The electron density map was established by multiple isomorphous replacement (m.i.r.; using 5 derivatives) and subsequent solvent-flattening at 2.8 A resolution. The sequence was built into the well-defined regions of the m.i.r. map; this partial model was refined using a simulated annealing refinement method with phase restraints. Phase combination of m.i.r. phases and phases of the partial model allowed the completion of the model. The final refinement was based on 29,838 independent reflections in the 8 to 2.1 A resolution range. A final R-factor of 15.6% was obtained with a model obeying standard geometry within 0.014 A in bond lengths and 2.8 degrees in bond angles. The final model consists of all 496 amino acid residues, 1 calcium ion, 1 chloride ion and 353 water molecules. The model is described in detail; the calcium and chloride binding sites are characterized.

Animals↗
PubMed1993

[Value of plasma progesterone (rapid assay) during ovarian stimulation for in vitro fertilization using LHRH agonists and hMG].

We have studied all the cycles (= 276) induced for in vitro fertilization using a LHRH agonist and the hMG (113 short protocols, 163 long protocols) from 01.90 to 07.90 to know the plasmatic profiles of the estradiol (E2), of the LH and specially of the progesterone (P) between J-7 and the day of the hCG (= J0). We observe in the short protocol an elevation (effect flare up) and afterwards a fall concomitant of the P and of the LH up to J-5, J-6 (effect of pituitary down regulation), in the short and long protocols a progressive elevation of J-3 up to J0 of the P parallel to E2, so that the LH remain stable or decrease. The LH of J0 is higher in short protocol than in long protocol (10.14 +/- 2.9 versus 4.72 +/- 1.3 Ul/l, p < 0.00001). We found the same progressive elevation of the P of J-3 up to J0 in pregnant and not pregnant patients. The surveillance of the P coupled to the E2 and to the follicular ultrasonography could help in the choice of the day of the hCG and avoid a post-maturity of oocyte. The consequences of the elevation of P In the morning of J0 have been study for P levels < 1 ng/ml (73 cases) and P > or = 1 ng/ml (203 cases) and afterwards for progressive elevation of P levels (1.5-2-2.5-3 ng/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Crystallization and preliminary crystallographic study of an octa-heme cytochrome c3 from Desulfovibrio desulfuricans Norway.

An octa-heme cytochrome c3, isolated as a dimeric molecule of about 30 kDa from the anaerobic bacteria Desulfovibro desulfuricans Norway, has been crystallized in a form suitable for atomic resolution X-ray structural investigations. The crystals are trigonal, space group P3(1)21 (or its enantiomorph P3(2)21), with cell dimensions: a = b = 72.9 A c = 62.7 A. The asymmetric unit contains most probably one monomer and a solvent content of about 60%. Under this assumption, the crystallographic 2-fold axis relates the two subunits of the dimer. Diffraction extends to 2.0 A.

Crystallization↗
PubMed1992

Site-directed mutagenesis of tetraheme cytochrome c3. Modification of oxidoreduction potentials after heme axial ligand replacement.

The nature of the axial ligands of a heme group is an important factor in maintaining the oxidation-reduction potential of a c-type cytochrome. Cytochrome c3 from Desulfovibrio vulgaris Hildenborough contains four bis-histidinyl coordinated hemes with low oxidation-reduction potentials. Site-directed mutagenesis was used to generate a mutant in which histidine 70, the sixth axial ligand of heme 4, has been replaced by a methionine. The mutant protein was expressed in Desulfovibrio desulfuricans G200 at a level similar to the wild type cytochrome. A model for the three-dimensional structure of D. vulgaris Hildenborough cytochrome c3 was generated on the basis of the crystal structure of D. vulgaris Miyazaki cytochrome c3 in order to investigate the effects of the H70M mutation. The model, together with NMR data, suggested that methionine 70 has effectively replaced histidine 70 as the sixth axial ligand of heme 4 without significant alteration of the structure. A large increase of at least 200 mV of one of the four oxidation-reduction potentials was observed by electrochemistry and is interpreted in terms of structure/potential relationships.

Amino Acid Sequence↗
PubMed1992

[Tubal sterility. What treatment to propose: IVF or surgery?].

The results of IVF in cases of tubal sterility are compared with those of surgery (macro- or micro-surgery, coelio-surgery). This analysis includes a continuous series of 1051 attempted pregnancies in 640 women (with or mixed tubal sterility with or without endometriosis). After an average 1.64 attempts per patient, 220 women had achieved 241 pregnancies (pregnancy rate: 22.9% per puncture, 34.3% per woman). Of these 241 pregnancies, there were 172 (71.8%) which continued to term, 57 (23.6%) miscarriages and 11 (4.6%) ectopic pregnancies. The pregnancies carried to term were single pregnancies in 129 cases (74.6%), twin pregnancies in 37 cases (21.4%) and triple pregnancies in 7 cases (4%). The indication of coelio-surgery (or microsurgery) is justified in young women with no history of genital tuberculosis, tubal plasty or ectopic pregnancy and presenting with purely tubal sterility with a good prognosis. Restoration of patency after tubal sterilization remains a good indication for microsurgery in young women. In all other cases, indication is for IVF from the outset.

Adult↗
PubMed1991

Effect of limited proteolysis in the 8th loop of the barrel and of antibodies on porcine pancreas amylase activity.

The porcine pancreatic alpha-amylase is a (beta/alpha)8-barrel protein, containing domains A and B (peptide sequence 1-403) and a distinct C-domain (peptide sequence 404-496). Separation of the terminal C-domain from the A and B domains has been attempted by limited proteolysis in the hinge region. Subtilisin was found to hydrolyse amylase between residues 369 and 370 situated in the loop between the eighth beta-strand and alpha-helix. The cleaved amylase was isolated by chromatofocusing and found to retain about 60% of the activity of the native enzyme, while the isolated fragments were inactive. Antigen binding fragments prepared from polyclonal antibodies to native amylase and the CNBr-fragment P1 (peptide sequence 395-496) respectively, were tested for influence on the enzyme activity. Antibodies directed against P1 had no effect whereas antibodies against the peptide sequence 1-394 and amylase respectively inhibited hydrolysis of substrates having four or more glucose residues but not of shorter oligomaltosides. Crystallographic analysis revealed that changes in the region of residue 369 might affect the conformation of the active site as well as of a second binding site. This site, located on the enzyme surface, is proposed to be required for the hydrolysis of larger substrates.

Amylases↗
PubMed1987

Three dimensional structure of porcine pancreatic alpha-amylase at 2.9 A resolution. Role of calcium in structure and activity.

The crystal structure of porcine pancreatic alpha-amylase (PPA) has been solved at 2.9 A resolution by X-ray crystallographic methods. The enzyme contains three domains. The larger, in the N-terminal part, consists of 330 amino acid residues. This central domain has the typical parallel-stranded alpha-beta barrel structure (alpha beta)8, already found in a number of other enzymes like triose phosphate isomerase and pyruvate kinase. The C-terminal domain forms a distinct globular unit where the chain folds into an eight-stranded antiparallel beta-barrel. The third domain lies between a beta-strand and a alpha-helix of the central domain, in a position similar to those found for domain B in triose phosphate isomerase and pyruvate kinase. It is essentially composed of antiparallel beta-sheets. The active site is located in a cleft within the N-terminal central domain, at the carboxy-end of the beta-strands of the (alpha beta)8 barrel. Binding of various substrate analogues to the enzyme suggests that the amino acid residues involved in the catalytic reaction are a pair of aspartic acids. A number of other residues surround the substrate and seem to participate in its binding via hydrogen bonds and hydrophobic interactions. The 'essential' calcium ion has been located near the active site region and between two domains, each of them providing two calcium ligands. On the basis of sequence comparisons this calcium binding site is suggested to be a common structural feature of all alpha-amylases. It represents a new type of calcium-protein interaction pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Rubredoxin from Desulfovibrio gigas. A molecular model of the oxidized form at 1.4 A resolution.

The crystal structure of rubredoxin from the sulfate-reducing bacterium Desulfovibrio gigas has been determined at 1.4 A resolution (1 A = 0.1 nm) by X-ray diffraction methods; starting with a model of the isostructural rubredoxin from Desulfovibrio vulgaris. Refinement of the molecular model has been carried out by restrained least-squares techniques and Fourier series calculations. The present model includes a formyl at the N-terminal end and 121 possible sites for solvent molecules with full or partial occupancy, which corresponds to the modeling of nearly all the solvent medium. The crystallographic R factor against the data with 10 A greater than d greater than 1.4 A with F greater than 2 sig(F), is 0.136; and R = 0.140 when all the data are considered. The estimated average root-mean-square (r.m.s.) error on the positional parameters is about 0.12 A. The overall structural features of this molecule are close to those of the two highly refined rubredoxins from Clostridium pasteurianum and D. vulgaris. Superposition of these two molecules on the rubredoxin from D. gigas shows in both cases an overall r.m.s. deviation of 0.5 A for the atoms in the main-chain and of 0.4 A for the atoms in the side-chains that make up the hydrophobic core. The iron atom is co-ordinated to four cysteine sulfur atoms forming an almost regular tetrahedron, with Fe-SG distances ranging from 2.27 A to 2.31 A and angles varying from 103 degrees to 115 degrees. The intramolecular hydrogen-bonding pattern is quite comparable to those found in other proteins refined at high resolution. All the polar groups are involved in hydrogen bonds: intramolecular, intermolecular or with solvent molecules. The main structural differences from the other rubredoxins are in the nature and the distribution of some of the charged residues over the molecular surface. The possible influence of several structural factors on the intramolecular and intermolecular electron transfer properties such as the NH...SG bonds, the solvent exposure of the redox center, and the aromatic core is discussed. The conservation, during evolution, of a ring of acidic residues in the proximity of the FeSG4 center suggests that this ring may be implicated in the recognition processes between rubredoxins and their functional partners.

Desulfovibrio↗
PubMed1987

[Hysteroplasty in 1986. Technics and indications].

Hysteroplasty described by Bret in 1959 represents the procedure of choice in cases of bifid uterus with infertility secondary to repeated interruptions of pregnancy or complicated deliveries. This technique, of which we will remind the main steps, gives excellent results as demonstrated in a joint series from the Gynecological and Obstetrical Clinics of Hopital Edouard Herriot. In view of these good results, it seems that the indications of hysteroplasty should be broader than before in order to prevent the risks inherent in repeated interruptions of pregnancy and complicated deliveries.

Abortion, Spontaneous↗
PubMed1987

[Observations on the new progestational agents].

The purpose of this article will be to present informations regarding two new progestational++ medications: nomegestrol acetate (Lutenyl), and promegestone (Surgestone) in order to make use of them in our prescription habits. We will situate them in relation to various groups of progestative medications and present their specific properties and their tolerance. Finally, we will demonstrate their role in contraception and their effectiveness in the main indications of progestative medications.

Contraceptive Agents, Female↗
PubMed1982

Crystal structure and electron transfer properties of cytochrome c3.

The crystal structure of cytochrome c3 from the sulfate-reducing bacteria Desulfovibrio desulfuricans, Norway strain, has been determined through the fitting of the recently completed primary structure to a 2.5 A resolution electron density map. The phase calculations were based on three mercurial derivatives; anomalous scattering data were used to refine the four heme iron positions. A preliminary refinement of the molecular model has led to a conventional crystallographic R factor of 34%. Cytochrome c3 is folded in two structural domains with one heme in each, the two other heme moieties lying in a large groove dividing the molecule. The core of the protein is the compact four-heme cluster which presents a relatively high degree of solvent exposure. The structural pattern of redox centers suggests that electron transfer might occur through direct contacts between some of the heme groups, via the overlapping system of pi oribitals or via intervening amino acid side chains or both.

Cytochrome c Group↗
PubMedDate not supplied

Structure and sequence of the multihaem cytochrome c3.

The molecular structure of cytochrome c3 isolated from Desulfovibrio desulfuricans has been solved on the basis of its crystallographic determination at 2.5 A resolution and of an essentially complete sequence. The molecule consists of a single polypeptide chain wrapped around a very compact core of four non-parallel haems which present a relatively high degree of exposure to the solvent. Alignment of the amino acid sequences of cytochrome c3 from several species suggests that the structure reported here is characteristic of the cytochrome c3 group.

Amino Acid Sequence↗
PubMedDate not supplied

[In vitro fertilization failures related to a sperm hyperactivation defect: indication for microinjection?].

Development of hyperactivated motility is considered as necessary for penetration through zona pellucida. In a study concerning 114 IVF attempts, we could not establish a significant correlation between fertilization rate and hyperactivation rate (HA). On the contrary, most fertilization failures (16/21) we found for HA values < 10%. 10 of such couples could benefit of ICSI for the next attempt: fertilization rates were strictly similar to the general rate observed for ICSI in our group (48%).

Female↗