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51.
Edgar Vázquez-Contreras Nora Vázquez-Laslop Georges Dreyfus 《Journal of bioenergetics and biomembranes》1995,27(1):109-116
A functional F0F1 ATP synthase that contains the endogenous inhibitor protein (F0F1I) was isolated by the use of two combined techniques [Adolfsen, R., McClung, J.A., and Moudrianakis, E. N. (1975).Biochemistry
14, 1727–1735; Dreyfus, G., Celis, H., and Ramirez, J. (1984).Anal. Biochem.
142, 215–220]. The preparation is composed of 18 subunits as judged by SDS-PAGE. A steady-state kinetic analysis of the latent ATP synthase complex at various concentrations of ATP showed aV
max of 1.28mol min–1 mg–1, whereas theV
max of the complex without the inhibitor was 8.3mol min–1 mg–1. In contrast, theK
m
for Mg-ATP of F0F1 I was 148M, comparable to theK
m
value of 142M of the F0F1 complex devoid of IF1. The hydrolytic activity of the F0F1I increased severalfold by incubation at 60C at pH 6.8, reaching a maximal ATPase activity of 9.5mol min–1 mg–1; at pH 9.0 a rapid increase in the specific activity of hydrolysis was followed by a sharp drop in activity. The latent ATP synthase was reconstituted into liposomes by means of a column filtration method. The proteoliposomes showed ATP-Pi exchange activity which responded to phosphate concentration and was sensitive to energy transfer inhibitors like oligomycin and the uncouplerp-trifluoromethoxyphenylhydrazone. 相似文献
52.
Abousalham Abdelkarim; Teissere Marcel; Gardies Anne-Marie; Verger Robert; Noat Georges 《Plant & cell physiology》1995,36(6):989-996
Phospholipase D (phosphatidylcholine phosphatidohydrolase EC3.1.4.4
[EC]
) from soybean (Glycine max L.) suspension-cultured cellwas purified around 1,200-fold to homogeneity by acetone precipitation,Macro-Prep High Q anion exchange, and octyl-Sepharose CL-4Baffinity chromatography. The purified enzyme released 1,600µmol of choline per min per mg of protein. The enzymeis monomeric with a molecular mass of 92 kDa, as estimated bySDS-PAGE. One of the most interesting characteristics of thepurified soybean phospholipase D was the dependence of the pHoptimum on the Ca2+ ion concentration in the assay. With 10mM, 20 mM and 40 mM Ca2+ ions, the optima were at pH 7.5, 6and 5.5, respectively. The specific adsorption of phospholipaseD onto octyl-Sepharose gel suggests that the molecule becomesmore hydrophobic in the presence of Ca2+ ions. The amino acidsequence of the first 18 N-terminal residues of soybean phospholipaseD revealed a high degree of homology with those previously publishedfor cabbage leaf and castor bean endosperm enzymes. Westernblots of the soybean phospholipase D showed an immunoreactivitywith antibodies raised against a synthetic peptide correspondingto the 15 N-terminal aminoacid residues of phospholipase D fromcabbage leaves. (Received March 13, 1995; Accepted May 29, 1995) 相似文献
53.
Mona El Agoze Marylène Poirié Georges Périquet 《Entomologia Experimentalis et Applicata》1995,75(3):251-255
In most insect species where double matings occur, sperm from the second male preferentially fertilize subsequent eggs. However,
we demonstrate here that, as already shown for some other hymenopteran species, this is not the case in the ichneumonid waspDiadromus pulchellus (Wesmeal): sperm from the first male usually father all the female progeny. This precedence of the first male sperm is also
observed in double matings involving an haploid male and a diploid sterile male, whichever is the first mating male. We discuss
the consequences of this phenomenon from an evolutionary point of view. 相似文献
54.
55.
Characterization of Calpain-Mediated Proteolysis of GluR1 Subunits of α-Amino-3-Hydroxy-5-Methylisoxazole-4-Propionate Receptors in Rat Brain 总被引:1,自引:0,他引:1
Xiaoning Bi Jing Chen Sandeeb Dang Robert J. Wenthold Georges Tocco Michel Baudry 《Journal of neurochemistry》1997,68(4):1484-1494
Abstract: Previous results have indicated that GluR1 subunits of α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors are targets of calpain. In the present study, we determined the effects of calpain treatment of synaptic membranes on GluR1 subunits using western blots with antibodies directed against the C-terminal (C-Ab) and the N-terminal (N-Ab) domains of the proteins, and compared them with the effects of calcium treatment of frozen-thawed brain sections. Calpain treatment of synaptic membranes resulted in a large decrease in the GluR1 band (105 kDa) labeled with C-Ab and in the formation of a doublet band labeled with N-Ab due to the appearance of a new species of GluR1 (98 kDa). These effects were blocked almost completely by calpain inhibitors. Calpain-induced changes in GluR1 immunological properties were not associated with modifications of [3 H]AMPA or 6-cyano-7-[3 H]nitroquinoxaline-2,3-dione ([3 H]CNQX) binding. Treatment of frozen-thawed brain sections with concentrations of calcium as low as 0.2 m M resulted in a large decrease in the 105-kDa GluR1 band and in the concurrent appearance of the 98-kDa band. This treatment was associated with increased [3 H]AMPA and [3 H]CNQX binding. These results suggest that there exist several types/states of GluR1 subunits exhibiting different sensitivities to calpain. Our data also indicate the existence of additional calcium-dependent processes regulating the characteristics of receptors in intact tissues. 相似文献
56.
57.
The enterotoxin gene (cpe) of Clostridium perfringens can be chromosomal or plasmid-borne 总被引:3,自引:0,他引:3
Emmanuel Cornillot † Brigitte Saint-Joanis Georges Daube Sei-ichi Katayama Per Einar Granum Bruno Canard ‡ Stewart T. Cole 《Molecular microbiology》1995,15(4):639-647
The location of the cpe gene, encoding the enterotoxin responsible for food poisoning in humans, has been studied in a series of enterotoxigenic Ciostridium perfringens strains by means of pulsed field gel electrophoresis of genomic DNA. The cpe gene was found at the same chromosomal locus in strains associated with food poisoning in humans and was shown to be linked to a repetitive sequence, the Hin dlll repeat, and an open reading frame, ORF3, that may be part of an insertion sequence. In contrast, when the strains originated from domesticated livestock cpe was located on a large episome where it was often close to a copy of the transposable element IS 1151. In these cases, the Hin dlll repeat was not linked to the cpe gene although this was generally preceded by ORF3. 相似文献
58.
Matthew J. Friedman Ante M. Krstulović Henri Colin Georges Guiochon Kathleen Pajer 《Analytical biochemistry》1984,142(2):480-486
Described in this paper is a rapid, isocratic assay for serum indole-3-acetic acid (IAA). The sample preparation involves only protein precipitation using sulfosalicylic acid, and the sensitivity of amperometric detection is in the picogram range. The chromatographic analysis time is approximately 4 min. The devised method was used for a longitudinal study of IAA levels in serum samples from control subjects and newly abstinent alcoholics. Dietary variations were eliminated by administering a 2.0-g loading dose of L-Trp to all subjects investigated. The results are presented in the form of cumulative frequency polygons. Preliminary data indicate no differences in IAA levels between newly abstinent alcoholics and control subjects. 相似文献
59.
Contact of adjacent root hairs of seedlings of white clover ( Trifolium repens L. cv. Ladino and Louisiana Nolin) led to cell-cell adhesion of root hair tips. The involvement of the root lectin, trifoliin A, in this phenomen was examined in slide cultures of axenically grown seedlings. Trifoliin A was detected by indirect immunofluorescence on root hair tips, which had adhered to one another. Seedlings grown under conditions which specifically reduce the levels of this lectin on the root surface (e.g., in the presence of 15 m M NO3 – or 5 m M 2-deoxy- d -glucose) had significantly fewer adhesions of root hair tips. In addition, flushing the slide cultures with 20 m M 2-deoxy- d -glucose resulted in an immediate 4-fold reduction in frequency of tip adhesions. These results are consistent with the lectin cross-bridging model, which predicts that cell-cell adhesions would occur when trifoliin A on root hair tips contacts complementary glycosylated receptors on neighboring root hairs. 相似文献
60.
Georges Olivier 《Journal of human evolution》1980,9(8):645-649
This study is divided in two parts. The first shows that the secular trend of increasing height is far from decreasing and, on the contrary, is accelerating. The second part attacks the problem of the causes of this phenomena. It shows that the increase of stature is linked to all indicators of the conditions of life, without any one factor being predominant. On the other hand, students of the more privileged back-grounds keep on showing this secular trend, though their life standards seems to be at the optimum. Therefore, the cause and the end of this phenomena cannot be demonstrated. 相似文献