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1.
Acetylcholinesterase is found in the brush-border and basolateral membranes purified from rabbit enterocytes. The sedimentation coefficients of the enzymes solubilized from two types of membrane are identical (5.5 +/- 0.2 S) and the apparent molecular weights are not significantly different (154 000 +/- 8000 for the brush-border and 145 000 +/- 8000 for the basolateral membrane enzyme). These results suggest a unique G2 molecular form for acetylcholinesterase from brush-border as well as from basolateral membranes. 相似文献
2.
A method has been developed for the study of somatostatin (SS) binding to dissociated cells from rat cerebral cortex. Binding of [125I][Tyr11]SS to cells obtained by mechanical dissociation of rat cerebral cortex was dependent on time and temperature, saturable, reversible and highly specific. Under conditions of equilibrium, i.e., 60 min at 25°C, native SS inhibited tracer binding in a dose-dependent manner. The Scatchard analysis of binding data was linear and yielded a dissociation constant of 0.60±0.08 nM with a maximal binding capacity of 160±16 fmol/mg protein. The binding of [125I][Tyr11]SS was specific as shown in experiments on tracer displacement by the native peptide, SS analogues, and unrelated peptides. 相似文献
3.
Meiosis reinitiation as a model system for the study of cell division and cell differentiation 总被引:2,自引:0,他引:2
In this paper, we review our findings concerning the control of meiosis reinitiation in starfish oocytes and discuss recent advances that lead to characterization of the maturation promoting factor (MPF) responsible for G2-M transition. It is now agreed that appearance of this factor, which triggers nuclear envelope breakdown, chromosome condensation and metaphase spindle formation, corresponds to the activation of a M-phase specific H1-kinase. MPF has been shown to be constituted of equimolar amounts of a 34 kDa catalytic subunit protein homologous to the yeast cdc2/CDC28 gene product and a cyclin protein homologous to the yeast cdc13 gene product. "In vivo" and "in vitro" studies based on the use of inhibitors of protein synthesis, protein kinases, phosphoprotein phosphatases and proteases lead to a better understanding of the complex series of events which regulate activation and inactivation of MPF. In the unfertilized metaphase 2-arrested vertebrate oocyte, it has also been shown that stabilization of MPF depends on the kinase activity of the c-mos protooncogene. This review attempts to illustrate how the significant progress made in the understanding of the regulation of cell cycle transverse directly resulted from the convergence of observations in multidisciplinary studies in yeast genetics, development and oncogenesis. It also offers a model for considering the highly integrated events which, starting at the level of the plasma membrane, may eventually result in early cell differentiation. 相似文献
4.
Sylvie Leparoux Marc Padrines Yannick Fortun Bernard Colas 《Biotechnology letters》1996,18(2):135-138
Summary Enzymatic O-glycosylation of dipeptide derivatives containing a serine residue in the N or C terminal position and alanine or glycine as the second amino acid was achieved using the transgalactosylation activity of -galactosidase from the Achatina achatina digestive juice. Reactions were performed with lactose as glycosyl donor and the dipeptide ethyl (or methyl) esters N-protected by a benzyloxycarbonyl group (Z) as glycosyl acceptors. Yields of galactosyl-dipeptide derivatives were much higher than those obtained with the E.coli -galactosidase as catalyst. 相似文献
5.
Expression and maturation of human foamy virus Gag precursor polypeptides. 总被引:4,自引:3,他引:1 下载免费PDF全文
In this report, we address the processing of the Gag polypeptides of human foamy virus previously reported to be atypical. In the cytoplasm or the nucleus of infected cells as well as in free virus particles, two Gag precursor polypeptides were identified at approximately 72 and 68 kDa, p72 giving rise to p68 by a maturation process. Efficient maturation of Gag precursors was observed only in two situations: (i) during the early steps of virus adsorption and (ii) under experimental conditions, including treatment with DNase I, known to dissociate actin polymers associated with high ionic strength and ionic detergents. Rather than being a defective viral protease function, an association of Gag precursors with a cytoskeleton network might be responsible for the low rate of Gag protein maturation through inhibition of their cleavage by the protease. 相似文献
6.
The purpose of this work was to facilitate the on-farm use of frozen semen by initially thawing the straws in laboratory treated sperm (TS) rather than on-farm control sperm (CS), as is usually done. After thawing, TS was diluted, centrifuged, and extended in skim milk for storage at +15° C until utilized 3 to 6 hours later. : immediately after preparation and addition of skim milk for TS and thawing for CS, the percentage of stained cells and abnormal cells was higher (P < 0.01) in TS than in CS. In contrast, following a 3 hour incubation, TS and CS had the same proportion of motile cells. : fertility and prolificacy of FGA + PMSG-treated ewes were slightly higher following AI (1 AI/female) with TS than with CS: 52.4% 44.2% and 155.0% 148.0%, respectively. Fertility was also higher (P < 0.01) with fresh semen than with TS, but the difference was only 9.2 points (70.3% 61.1% for the respective 798 and 242 ewes inseminated once). Prolificacy rates were similar (164.3% 167.6%). 相似文献
7.
S Knuhtsen J P Esteve C Cambillau B Colas C Susini N Vaysse 《The Journal of biological chemistry》1990,265(2):1129-1133
Somatostatin receptors were solubilized from rat pancreatic membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonic acid (CHAPS). The binding of an iodinated somatostatin analog [125I-Tyr3]SMS to the soluble fraction was time-dependent, saturable, and reversible. Scatchard analysis of equilibrium binding data indicated that the soluble extract contained a single class of somatostatin binding sites with a Kd of 0.3 nM and a Bmax of 210 fmol/mg. As observed with membrane-bound receptors, soluble binding receptors were sensitive to the GTP analog GTP gamma S indicating that they are functionally linked to a G protein. A molecular weight of about 400,000 was determined for soluble receptors under native conditions by gel filtration. In denaturing gel electrophoresis, photoaffinity labeling of soluble receptors identified a major protein of Mr = 100,000 and two minor proteins of Mr = 56,000 and 21,000. Isoelectric focusing of soluble receptors revealed that the somatostatin receptor is an acidic protein with pI 4.8. The soluble somatostatin receptor is a glycoprotein which can be specifically bound to the wheat germ agglutinin lectin and eluted by triacetyl-chitotriose. 相似文献
8.
C Saunier R Hennequin B Hannhart P Horsky T Garcia Carmona T Colas 《Comptes rendus des séances de la Société de biologie et de ses filiales》1975,169(1):136-140
An increase in H+ ions concentration by infusion of hydrochloric acid produces a reduction in lactacidemia. This phenomenon is a result of the inhibitory effect of acidosis on phosphofructokinase producing a diminution of intracellular glycolysis. 相似文献
9.