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J Garnier

Publications and source records attributed to J Garnier.

At least 73 records · Page 4Linked to original sources
PubMed1987

Further developments of protein secondary structure prediction using information theory. New parameters and consideration of residue pairs.

We have re-evaluated the information used in the Garnier-Osguthorpe-Robson (GOR) method of secondary structure prediction with the currently available database. The framework of information theory provides a means to formulate the influence of local sequence upon the conformation of a given residue, in a rigorous manner. However, the existing database does not allow the evaluation of parameters required for an exact treatment of the problem. The validity of the approximations drawn from the theory is examined. It is shown that the first-level approximation, involving single-residue parameters, is only marginally improved by an increase in the database. The second-level approximation, involving pairs of residues, provides a better model. However, in this case the database is not big enough and this method might lead to parameters with deficiencies. Attention is therefore given to overcoming this lack of data. We have determined the significant pairs and the number of dummy observations necessary to obtain the best result for the prediction. This new version of the GOR method increases the accuracy of prediction by 7%, bringing the amount of residues correctly predicted to 63% for three states and 68 proteins, each protein to be predicted being removed from the database and the parameters derived from the other proteins. If the protein to be predicted is kept in the database the accuracy goes up to 69.7%.

Amino Acid Sequence↗
PubMed1987

Studies on rationales for an expert system approach to the interpretation of protein sequence data. Preliminary analysis of the human epidermal growth factor receptor.

The molecular modelling of larger proteins benefits from a preliminary analysis of the sequence to identify regions of potential structural and functional importance. In this study the sequence of the epidermal growth factor receptor has been analysed using a variety of established methods and novel procedures developed for the study of weak internal and external homologies and for the use of homologous sequences in the prediction of secondary and super-secondary structures. The procedures explored here are potentially suitable for incorporation into an expert system for the initial investigation of protein sequence data.

Amino Acid Sequence↗
PubMed1987

Internalization and recycling of lutropin receptors upon stimulation by porcine lutropin and human choriogonadotropin in porcine Leydig cells.

Porcine lutropin (pLH) and human choriogonadotropin (hCG) recognize the same hormonal receptor and elicit the same steroidogenic response in porcine Leydig cells in primary culture. We compared the variation in the number of occupied and free receptors present on the cell surface under short-term stimulation by the two hormones at 35 degrees C. Both hormones produced a rapid dose-dependent decrease in the total number of the gonadotropin receptors present on the cell surface with a half-life of 8-10 min. This decrease was reversible upon hormone removal and receptors were recovered on the cell surface with the same half-life of 8-10 min. With pLH, the receptors were recycled in a free state, but in the presence of hCG the receptors were recycled in an occupied state. This difference could be related to the higher affinity of hCG for the receptor in 150 mM NaCl buffer (Ka = 1.6 X 10(9) for hCG and 1.5 X 10(7) for pLH) and higher stability to acid pH of the hCG-receptor complex (dissociation pK = 3.7 for hCG and 4.5 for pLH).

Animals↗
PubMed1986

An algorithm for secondary structure determination in proteins based on sequence similarity.

A secondary structure prediction algorithm is proposed on the hypothesis that short homologous sequences of amino acids have the same secondary structure tendencies. Comparisons are made with the secondary structure assignments of Kabsch and Sander from X-ray data [(1983) Biopolymers 22, 2577-2637] and an empirically determined similarity matrix which assigns a sequence similarity score between any two sequences of 7 residues in length. This similarity matrix differs in many respects from that of the Dayhoff substitution matrix [(1978) in: Atlas of Protein Sequence and Structure, (Dayhoff, M.O. ed). vol. 5. suppl. 3, pp. 353-358, National Biochemical Research Foundation, Washington, DC]. This homologue method had a prediction accuracy of 62.2% over 3 states for 61 proteins and 63.6% for a new set of 7 proteins not in the original data base.

Amino Acid Sequence↗
PubMed1986

[A high-capacity affinity gel for the purification of the testicular lutropin receptor].

The lutropin (LH) receptor from porcine testes was solubilized with 1% Triton X-100. The final solution was centrifuged at 100,000 X g and the supernatant was concentrated on a PM30 Amicon membrane. The concentrate was then specifically retained on an affinity gel with human choriogonadotropin (hCG) covalently grafted by its sugar moiety. The agarose affinity gel bore adipic acid hydrazide spacer arms (6 carbon length). Prior to coupling, the subunits of hCG were crosslinked with 1-ethyl-3-(dimethylamino propyl) carbodiimide and the sialic acid residues were subjected to periodate oxidation to yield aldehyde groups which could react with the hydrazides of the gel. 90% of the receptor contained in the solution incubated with this gel was retained and eluted at pH 3.2 with a purification factor greater than 700, versus a 26% yield and a purification factor of 40 with an affinity gel bearing hCG linked through its lysine epsilon-amines.

Animals↗
PubMed1985

Prediction of the conformation and antigenic determinants of the V-sis viral oncogene product homologous with human platelet-derived growth factor.

In an extensive study involving unification of secondary structure prediction methods to predict peptide backbone angles, folding simulations, and interactive graphics we have calculated conformations for a 160 residue p28sis protein fragment. We demonstrate that the state of the art is sufficient to aid artificial vaccine design.

Antigens, Viral↗
PubMed1984

Adenylate cyclase and membrane fluidity. The repressor hypothesis.

The relationships between membrane fluidity as induced by drug addition and the stimulation of adenylate cyclase by hormones (mainly catecholamines), GTP, Gpp(NH)p and NaF are reviewed. In particular, the data corresponding to pigeon erythrocyte membranes are reviewed and compared with other data published in the literature. A brief summary of the theories involved in fluidity measurements and their significance at the molecular level is also given for anisotropy of fluorescence and electron spin resonance. One of the conclusions is that the cationic drugs and neutral alcohols by perturbing preferentially the inner half-layer of the bilayer induced in pigeon erythrocyte membrane correlated multiphasic changes on fluidity and adenylate cyclase activity. This and other experimental data concerning the regulation of the adenylate cyclase are discussed in regard to a new interpretation of cyclase stimulation: the repressor hypothesis. In cell membrane the catalytic unit C is repressed by its association with a repressor complex made of the hormone receptor R and the regulatory protein N. The activation of cyclase activity is the dissociation of the catalytic unit C from the repressor complex R.N according to the equilibrium: R.N.C (inactive) in equilibrium R.N + C (active). Hormones, metal ions (magnesium), and nucleotides (GTP) are the allosteric ligands which shift this equilibrium towards the dissociation state with the liberation of the active form, membrane-bound, C unit. Gpp(NH)p, fluoride and forskolin will also shift the equilibrium toward the right. GDP and free receptors favour the associated repressed state of the system.

Adenylyl Cyclases↗
PubMed1983

[Multicentric reticulohistiocytosis. A new case].

Multicentric reticulohistiocytosis is a rare disorder of the skin and joints that possesses distinctive histologic findings. A case is reported with typical features, and ulceration, an unusual outcome of "skin" lesions.

Aged↗
PubMed1983

Lutropin is processed much more rapidly than human choriogonadotropin by porcine Leydig cells in primary culture.

Lutropin (LH) and human choriogonadotropin (hCG) share the same receptor and stimulate testosterone production in porcine Leydig cells in primary culture. Cells were pulsed with [125I]LH or [125I]hCG. During the chase, more than 80% of cell-bound LH consisted in internalized material which was degraded and excreted (half-time : 25 min) NH4Cl largely inhibited this degradation. On the contrary, hCG remained essentially bound to the cell surface and was not degraded by the cells with or without NH4Cl up to 160 min.

Animals↗
PubMed1983

[Isolated retroperitoneal hydatid cyst. Apropos of 2 new cases].

Hydatid disease in endemic countries is common but an isolated retroperitoneal localisation is rare. After a review of the aetiopathogenesis and clinical aspects, the authors express the opinion that safe, rapid and reliable technique of echotomography is the key investigation in obtaining a positive diagnosis. In terms of its course, the histopathological appearances are those of a locally malignant tumour which as a preferential and severe effect on renal function. Surgery is the only valid method for eradication of the parasite and freeing the urinary tract.

Adolescent↗
PubMed1982

Modulation of adenylate cyclase activity by the physical state of pigeon erythrocyte membrane. 1. Parallel drug-induced changes in the bilayer fluidity and adenylate cyclase activity.

The fluorescence anisotropy probe perylene and the spin-labels 5-doxylsterate and 16-doxylstearate were used to estimate the order and internal microviscosity of the pigeon erythrocyte membrane upon perturbation by cationic or neutral amphipathic drugs (chlorpromazine, methochlorpromazine, tetracaine, and octanol) and an anionic drug, octanoic acid. Both methods gave identical results. The fluidity changes were found to strictly correlate with those of adenylate cyclase activity in the presence of GTP when perturbed by the drugs [Salesse, R., & Garnier, J. (1979) Biochim. Biophys. Acta 554, 102-113]. The cationic or neutral drugs, in an intermediate range of concentration, decreased the degree of organization and the internal microviscosity of the lipids together with the activity of the adenylate cyclase. At a higher concentration they reincreased them up to or higher than their initial level before the final destruction of the membrane structure and functions. This concentration effect was time dependent with tetracaine. The quaternary amine methochlorpromazine acted as chlorpromazine only on open ghosts. On intact cells, it inhibited catecholamine receptors at higher concentration and monotonously decreased the order and microviscosity, as the anionic amphipath octanoic acid did. This is taken as evidence that the inner leaflet of the bilayer is the seat for the observed multiphasic changes of viscosity and the control of adenylate cyclase and catecholamine receptors. This could stem from either a preferential intercalation or a surface effect of the amphipaths in the inner leaflet of the membrane. Since the basal activity of adenylate cyclase was not affected in the presence of drugs, it may be inferred that the enzyme holds its activity but that its stimulation is modulated by the membrane physical state.

1-Octanol↗
PubMed1982

Modulation of adenylate cyclase activity by the physical state of pigeon erythrocyte membrane. 2. Fluidity-controlled coupling between the subunits of the adenylate cyclase system.

In the preceding paper, we described the parallel effect of amphipathic drugs on the fluidity and adenylate cyclase activity of pigeon erythrocyte membrane. This parallelism was found when the cyclase activity was assayed in the presence of a guanyl nucleotide and with Mg-ATP as the substrate after a preincubation of the membrane with the drugs [Salesse, R., Garnier, J., Leterrier, F., Daveloose, D., & Viret, J. (1982) Biochemistry (preceding paper in this tissue)]. However, when the regulatory protein (N) and the catalytic unit (E) were precoupled by GppNHp or fluoride before the action of the drugs, the cyclic AMP production was never inhibited. Thus, the drug-induced fluidization appeared to interfere with the efficiency of the activating coupling between N and E. Chlorpromazine even enhanced the cyclase activity: if the catecholamine receptor (R) repressed the cyclase activity in the absence of hormone [Rodbell, M. (1980) Nature (London) 284, 17-22], the loss of R molecules with chlorpromazine would prevent this inhibition and lead to hyperactivity of the enzyme. On the other hand, the comparison between two states of the adenylate cyclase system, (1) N and E reversibly precoupled in the presence of GTP and (2) R, N, and E precoupled in the presence of GTP plus isoproterenol, showed no difference between the activity curves at various drug concentrations: this may be interpreted as a permanent coupling of R and N. The main control exerted by fluidity on the activity of the adenylate cyclase system would thus be at the level of the activating coupling between the N subunit and the catalytic unit in pigeon erythrocyte membrane.

1-Octanol↗
PubMed1981

Physico-chemical properties of pregnant mare serum gonadotropin.

Pregnant mare serum gonadotropin exhibits a dissociation at acid pH as shown by the drop of s20,w values from 3.52 S at pH 8.1 to 2.52 S at pH 2.0. The dissociation is accompanied by an absorbance change with a maximum at 287 nm and a parallel loss of both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) activities as followed by radioreceptor assays. The apparent pKa of the acid transition is 3.45 with an extremely slow and temperature-dependent rate at pH 2.0 (1.8 . 10(-4) s-1 at 37 degrees C). By gel filtration the molecular weight of the active hormone is estimated to be 45 000 (rather than the previously reported 53 000-64 000). The active conformation of the hormone includes beta sheet structure (34%) as for other gonadotropin hormones with a minor but significative amount of alpha-helix. Four tyrosine residues were titrated, two of pKa = 10.3 and two of pKa = 11 out of a total of seven tyrosines. The parallel changes in FSH and LH activities during the preparation and the acid transition suggest that the two biological activities are intrinsic properties of the same molecular entity.

Animals↗