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排序方式: 共有96条查询结果,搜索用时 15 毫秒
1.
Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones 总被引:1,自引:1,他引:0
A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer. 相似文献
2.
Cryoelectron microscopy of frozen-hydrated alpha-ketoacid dehydrogenase complexes from Escherichia coli 总被引:1,自引:0,他引:1
The native architectures of the pyruvate and 2-oxoglutarate dehydrogenase complexes have been investigated by cryoelectron microscopy of unstained, frozen-hydrated specimens. In pyruvate dehydrogenase complex and 2-oxoglutarate dehydrogenase complex the transacylase (E2) components exist as 24-subunit, cube-shaped assemblies that form the structural cores of the complexes. Multiple copies (12-24) of the alpha-ketoacid dehydrogenase (E1) and dihydrolipoyl dehydrogenase (E3) components bind to the surface of the cores. Images of the frozen-hydrated enzyme complexes do not appear consistent with a symmetric arrangement of the E1 and E3 subunits about the octahedrally symmetric E2 core. Often the E1 or E3 subunits appear separated from the surface of the E2 core by 3-5 nm, and sometimes thin bridges of density appear in the gap between the E2 core and the bound subunits; studies of subcomplexes consisting of the E2 core from 2-oxoglutarate dehydrogenase complex and E1 or E3 show that both E1 and E3 are bound in this manner. Images of the E2 cores isolated from pyruvate dehydrogenase complex appear surrounded by a faint fuzz that extends approximately 10 nm from the surface of the core and likely corresponds to the lipoyl domains of the E2. 相似文献
3.
Christiane Lacombe Viviane Viallard Stphane Schaak Herv Paris 《Biology of the cell / under the auspices of the European Cell Biology Organization》1996,88(3):123-129
Summary— As evidenced by pertussis toxin-catalysed [32P]ADP-ribosylation, immunoblotting and Northern blot, the human adenocarcinoma intestinal cell line Caco-2 expresses Gi2 and Gi3 proteins. The localization of these two Gis within the cell was investigated by using subcellular fractionation and confocal microscopy on intact cell layer. A brush-border rich fraction and a pellet containing the remaining cellular membranes were prepared. [32P]ADP-ribosylation and immunoblotting demonstrated the presence of both αi2 and αi3 in these two preparations. Immunofluorescence studies performed on intact cells grown on Transwell filters and viewed by confocal microscopy further confirmed the localization of αi3-subunit on basolateral as well as on apical membranes. In contrast, αi2-subunit was shown to accumulate mainly in the intra-cellular compartment while only faint staining of the plasma membrane was detectable. Based upon double-labelling experiments with antibody against rough endoplasmic reticulum (RER), there is a strong possibility that intra-cellular sites of αi2-subunit correspond to association with RER membranes. 相似文献
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6.
Irene Mittermann Jacquelyn S. Fetrow Diana L. Schaak Steven C. Almo Dietrich Kraft Erwin Heberle-Bors R. Valenta 《Sexual plant reproduction》1998,11(4):183-191
Profilins are structurally well conserved low molecular weight (12–15 kDa) eukaryotic proteins which interact with a variety
of physiological ligands: (1) cytoskeletal components, e.g., actin; (2) polyphosphoinositides, e.g., phosphatidylinositol-4,5-bisphosphate;
(3) proline-rich proteins, e.g., formin homology proteins and vasodilatator-stimulated phosphoprotein. Profilins may thus
link the microfilament system with signal transduction pathways. Plant profilins have recently been shown to be highly crossreactive
allergens which bind to IgE antibodies of allergic patients and thus cause symptoms of type I allergy. We expressed and purified
from Escherichia coli profilins from birch pollen (Betula verrucosa), humans (Homo sapiens) and yeast (Schizosaccharomyces pombe) and demonstrated that each of these profilins is able to form stable homo- and heteropolymers via disulphide bonds in vitro.
Circular dichroism analysis of oxidized (polymeric) and reduced (monomeric) birch pollen profilin indicates that the two states
have similar secondary structures. Using 125I-labeled birch pollen, yeast and human profilin in overlay experiments, we showed that disulphide bond formation between
profilins can be disrupted under reducing conditions, while reduced as well as oxidized profilin states bind to actin and
profilin-specific antibodies. Exposure of profilin to oxidizing conditions, such as when pollen profilins are liberated on
the surface of the mucosa of atopic patients, may lead to profilin polymerization and thus contribute to the sensitization
capacity of profilin as an allergen.
Received: 25 February 1998 / Revision accepted: 12 May 1998 相似文献
7.
Mutagenesis of histidine 26 demonstrates the importance of loop-loop and loop-protein interactions for the function of iso-1-cytochrome c.
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J. S. Fetrow U. Dreher D. J. Wiland D. L. Schaak T. L. Boose 《Protein science : a publication of the Protein Society》1998,7(4):994-1005
In yeast iso-1-cytochrome c, the side chain of histidine 26 (His26) attaches omega loop A to the main body of the protein by forming a hydrogen bond to the backbone atom carbonyl of glutamic acid 44. The His26 side chain also forms a stabilizing intra-loop interaction through a hydrogen bond to the backbone amide of asparagine 31. To investigate the importance of loop-protein attachment and intra-loop interactions to the structure and function of this protein, a series of site-directed and random-directed mutations were produced at His26. Yeast strains expressing these variant proteins were analyzed for their ability to grow on non-fermentable carbon sources and for their intracellular production of cytochrome c. While the data show that mutations at His26 lead to slightly decreased intracellular amounts of cytochrome c, the level of cytochrome c function is decreased more. The data suggest that cytochrome c reductase binding is affected more than cytochrome c oxidase or lactate dehydrogenase binding. We propose that mutations at this residue increase loop mobility, which, in turn, decreases the protein's ability to bind redox partners. 相似文献
8.
Baart GJ Zomer B de Haan A van der Pol LA Beuvery EC Tramper J Martens DE 《Genome biology》2007,8(7):R136
Background
Neisseria meningitidis is a human pathogen that can infect diverse sites within the human host. The major diseases caused by N. meningitidis are responsible for death and disability, especially in young infants. In general, most of the recent work on N. meningitidis focuses on potential antigens and their functions, immunogenicity, and pathogenicity mechanisms. Very little work has been carried out on Neisseria primary metabolism over the past 25 years. 相似文献9.
Eoghan M Cunnane John JE Mulvihill Hilary E Barrett Michael T Walsh 《Biomedical engineering online》2015,14(Z1):S7
Background
Due to the limited number of experimental studies that mechanically characterise human atherosclerotic plaque tissue from the femoral arteries, a recent trend has emerged in current literature whereby one set of material data based on aortic plaque tissue is employed to numerically represent diseased femoral artery tissue. This study aims to generate novel vessel-appropriate material models for femoral plaque tissue and assess the influence of using material models based on experimental data generated from aortic plaque testing to represent diseased femoral arterial tissue.Methods
Novel material models based on experimental data generated from testing of atherosclerotic femoral artery tissue are developed and a computational analysis of the revascularisation of a quarter model idealised diseased femoral artery from a 90% diameter stenosis to a 10% diameter stenosis is performed using these novel material models. The simulation is also performed using material models based on experimental data obtained from aortic plaque testing in order to examine the effect of employing vessel appropriate material models versus those currently employed in literature to represent femoral plaque tissue.Results
Simulations that employ material models based on atherosclerotic aortic tissue exhibit much higher maximum principal stresses within the plaque than simulations that employ material models based on atherosclerotic femoral tissue. Specifically, employing a material model based on calcified aortic tissue, instead of one based on heavily calcified femoral tissue, to represent diseased femoral arterial vessels results in a 487 fold increase in maximum principal stress within the plaque at a depth of 0.8 mm from the lumen.Conclusions
Large differences are induced on numerical results as a consequence of employing material models based on aortic plaque, in place of material models based on femoral plaque, to represent a diseased femoral vessel. Due to these large discrepancies, future studies should seek to employ vessel-appropriate material models to simulate the response of diseased femoral tissue in order to obtain the most accurate numerical results.10.