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1.
Assembly of the F1 portion of the proton-translocating ATPase of Escherichia coli was examined in vivo. Analysis of strains lacking genes which specify the Fo polypeptides a, b, and c showed that the F1 subunits were able to assemble into a complex in the absence of the Fo subunits. In addition we have investigated the effects of mutations in the individual genes which specify the F1 polypeptides on the assembly process. Mutations of the uncA(alpha), uncG(gamma), or uncD(beta) genes result in a defective assembly of the F1 complex. In contrast, mutations in the uncH(delta) or uncC(epsilon) genes did not prevent assembly of the core alpha beta gamma complex. In these cases, however, the partial F1 complexes were incapable of restoring energy-linked functions to F1-depleted membranes. 相似文献
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Intracellular transport of cholesterol to the plasma membrane 总被引:10,自引:0,他引:10
We have modified a plasma membrane isolation procedure which utilizes DEAE-Sephadex beads (Gotlib, L. J., and Searls, D. B. (1980) Biochim. Biophys. Acta 602, 207-212) to rapidly measure intracellular transport of cholesterol from the site of synthesis in the endoplasmic reticulum to the plasma membrane. This transport process is rapid, with a half-time of about 10 min, has different kinetics from that of intracellular glycoprotein transport, and appears to be energy-dependent. 相似文献
4.
Two cases of trisomy 16 confined to placental tissue associated with an unfavourable outcome of the pregnancy are reported. In the first case, after a diagnosis of an apparent non-mosaic trisomy 16 at chorionic villi sample (CVS), an intrauterine fetal death occurred at the 22nd week. In the second case a mosaic with trisomy 16 was found in chorionic villi and the fetus was still-born at 38 weeks. From a comparison of their cases with those of the literature, the authors conclude that a trisomy 16 confined to placental tissue has a negative effect on fetal growth and pregnancy outcome. 相似文献
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A hybrid gene has been constructed consisting of coding sequence for the membrane domain of the endoplasmic reticulum protein 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase linked to the coding sequence for the soluble enzyme Escherichia coli beta-galactosidase. Expression of the hybrid gene in transfected Chinese hamster ovary cells results in the production of a fusion protein (HMGal) which is localized in the endoplasmic reticulum. The fusion protein contains the high-mannose oligosaccharides characteristic of HMG-CoA reductase. Importantly the beta-galactosidase activity of HMGal decreases when low density lipoprotein is added to the culture media. Therefore, the membrane domain of HMG-CoA reductase is sufficient to determine both correct intracellular localization and sterol-regulation of degradation. Mutant fusion proteins which lack 64, 85, or 98 amino acid residues from within the membrane domain of HMG-CoA reductase are found to be localized in the endoplasmic reticulum and to retain beta-galactosidase activity. However, sterol-regulation of degradation is abolished. 相似文献
7.
I Ventrelli P Melandri M Torboli G Berti M Simoni T Sapigni 《Bollettino della Società italiana di biologia sperimentale》1991,67(1):89-96
Minced polyester threads introduced into peritoneal cavity of guinea pigs or rats cause a granulomatous inflammation with evidence of macrophage stimulation. Chemotactic agents play an important role in the inflammatory reaction; they may be exogenous and/or endogenous. These are released locally by the cells involved in inflammation. In this paper the chemotactic effects of the peritoneal fluids from rats bearing the polyester inflammatory process, have been studied on PMN cells "in vitro". The peritoneal cavity fluids were obtained by washing the cavity of untreated rats or rats intraperitoneally injected with polyester, 1, 3, 7, 14 days after the intraperitoneal injection. The chemotactic response was assayed by employing modified chemotaxis Boyden chambers (Blind Well Neuro Probe) and polymorphonuclear leukocytes from normal or treated rats. Quantification of the migration was calculated by chemotactic index (A/B) (B = random migration, A = chemotaxis). The results demonstrated that the peritoneal fluids taken 3 and 7 days after the intraperitoneal polyester injection, elicit an evident chemotaxis response greater than that showed by peritoneal fluids from control rats. It is suggested that chemotactic factors can be produced and released by mononuclear cells involved in the inflammatory process. 相似文献
8.
Proton translocation by the F1F0ATPase of Escherichia coli. Mutagenic analysis of the a subunit 总被引:7,自引:0,他引:7
Cassette site-directed mutagenesis was employed to generate mutations in the a subunit (uncB (a) gene) of F1F0ATP synthase. Using sequence homology with similar subunits of other F1F0ATP synthases as a guide, 20 mutations were targeted to a region of the a subunit thought to constitute part of the proton translocation mechanism. ATP-driven proton pumping activity is lost with the substitution of lys, ile, val, or glu for arginine 210. Substitution of val, leu, gln, or glu for asparagine 214 does not completely block proton conduction, however, replacement of asparagine 214 with histidine does reduce enzyme activity below that necessary for significant function. Two or three mutations were constructed in each of four nonpolar amino acids, leucine 207, leucine 211, alanine 217, and glycine 218. Certain specific mutations in these positions result in partial loss of F1F0ATP synthase activity, but only the substitution of arginine for alanine 217 reduces ATP-driven proton pumping activity to undetectable levels. It is concluded that of the six amino acids studied, only arginine 210 is an essential component of the proton translocation mechanism. Fractionation of cell-free extracts of a subunit mutation strains generally reveals normal amounts of F1 specifically bound to the particulate fraction. One possible exception is the arginine 210 to isoleucine mutation which results in somewhat elevated levels of free F1 detectable in the soluble fraction. For nearly all a subunit mutations, F1F0-mediated ATP hydrolysis activity remains sensitive to inhibition by dicyclohexylcarbodiimide in spite of the fact that the mutations block proton translocation. 相似文献
9.
Janaine Almeida Neto Daniel Amando Nery Katia Simoni Bezerra Lima Maria Eduarda Gomes da Cruz Silva Tarcísio Cícero de Lima Araújo Nathália Andrezza Carvalho de Souza Rodolfo Hideki Vicente Nishimura Camila de Souza Araújo Ana Paula de Oliveira Jackson Roberto Guedes da Silva Almeida Larissa Araújo Rolim 《化学与生物多样性》2023,20(3):e202201039
This article describes the phytochemical study of Cannabis sativa roots from northeastern Brazil. The dried plant material was pulverized and subjected to exhaustive maceration with ethanol at room temperature, obtaining the crude ethanolic extract (Cs-EEBR). The volatile compounds were analyzed by gas chromatography coupled with mass spectrometry (GC/MS), which allowed to identify 22 compounds by comparing the linear retention index (LRI), the similarity index (SI) and the fragmentation pattern of the constituents with the literature. By this technique the major compounds identified were: friedelan-3-one and β-sitosterol. In addition, two fractions were obtained from Cs-EEBR by classical column chromatography and preparative thin layer chromatography. These fractions were analyzed by NMR and IR and together with the mass spectrometry data allowed to identify the compounds: epifriedelanol, friedelan-3-one, β-sitosterol and stigmasterol. The study contributed to the phytochemical knowledge of Cannabis sativa, specifically the roots, as there are few reports on the chemical constituents of this part of the plant. 相似文献
10.
S. Simoni R. Cantini† M. Castagnoli A. Battisti‡ 《Agricultural and Forest Entomology》2004,6(3):175-180
Abstract 1 In the Mediterranean region, the eriophyoid mite Trisetacus juniperinus causes considerable damage to the evergreen cypress, Cupressus sempervirens L., particularly in nurseries and young stands, disturbing the apical growth of the tree. 2 The impact of mites on survival and apical growth of two commercial clones of cypress (Agrimed and Bolgheri), as well as the results of differently timed pesticide applications to suppress mite population on newly grafted trees, were evaluated. 3 Mites easily infested clonal scions from rootstocks that were previously infested in the nursery, inducing tip deformation and disturbance of the growth. Apical growth was significantly lower in infested than in control trees 2 years following the graft. 4 Deformed apical buds were left early by mites, which dispersed in the crown and may have incurred high mortality. This is interpreted as a defensive reaction of the cypress to the mite attack, which involves costs resulting in reduced apical growth in both clones. However, mites partly overcame tree defences in the Bolgheri clone. 5 Healthy rootstock and graft material should be used to limit damage and maintain plant growth because natural infestations rarely occur. In case of attack, a pesticide should be applied as soon as possible because precocious mite infestation has a log‐lasting effect on tree growth, with considerable economic damage. 相似文献