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1.
M Irving 《BMJ (Clinical research ed.)》1981,283(6295):847-849
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Caveolin induces membrane curvature and drives the formation of caveolae that participate in many crucial cell functions such as endocytosis. The central portion of caveolin-1 contains two helices (H1 and H2) connected by a three-residue break with both N- and C-termini exposed to the cytoplasm. Although a U-shaped configuration is assumed based on its inaccessibility by extracellular matrix probes, caveolin structure in a bilayer remains elusive. This work aims to characterize the structure and dynamics of caveolin-1 (D82–S136; Cav182–136) in a DMPC bilayer using NMR, fluorescence emission measurements, and molecular dynamics simulations. The secondary structure of Cav182–136 from NMR chemical shift indexing analysis serves as a guideline for generating initial structural models. Fifty independent molecular dynamics simulations (100 ns each) are performed to identify its favorable conformation and orientation in the bilayer. A representative configuration was chosen from these multiple simulations and simulated for 1 μs to further explore its stability and dynamics. The results of these simulations mirror those from the tryptophan fluorescence measurements (i.e., Cav182–136 insertion depth in the bilayer), corroborate that Cav182–136 inserts in the membrane with U-shaped conformations, and show that the angle between H1 and H2 ranges from 35 to 69°, and the tilt angle of Cav182–136 is 27 ± 6°. The simulations also reveal that specific faces of H1 and H2 prefer to interact with each other and with lipid molecules, and these interactions stabilize the U-shaped conformation. 相似文献
4.
This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies
by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related
cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published
work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord.
Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement
by non-notochordal cells. 相似文献
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Nonlymphoid, stromal cells in the mouse thymus are believed to be important in T cell maturation and have been proposed to play a central role in the acquisition of major histocompatibility complex (MHC) restriction and self-tolerance by maturing thymocytes. Both cortical and medullary epithelial cells in the thymus express high levels of class II (A) major histocompatibility antigens (MHC Ags). We show here that a specific subset of these A– epithelial cells express a transformation-associated antigen (6C3Ag) found previously on the surfaces of Abelson murine leukemia virus-transformed pre-B cells and on those bone marrow-derived stromal cell clones which support normal and preneoplastic pre-B cell proliferation. Among solid lymphoid organs, only the thymus contains 6C3Ag1 cells and within the thymus, this antigen is found exclusively on A– epithelial cells in cortical regions. It is striking that the expression of the 6C3Ag on thymic epithelium is developmentally regulated, suggesting a role for this lymphostromal antigen in the maturation of the thymic microenvironment. 相似文献
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When HL-60 cells are induced to differentiate by dimethyl sulfoxide along a granulocytic pathway there is a fivefold decrease in the total number of transferrin receptors within 3 days, as compared to untreated cells. This decrease is due primarily to a rapid decline in the synthesis of the receptor rather than an increase in the degradation of the receptor. The decrease in transferrin receptor synthesis is a specific and early event that precedes the cessation of cell proliferation, differentiation, and the decrease in total protein synthesis. 相似文献
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Phosphatidylcholine breakdown in rat liver plasma membranes. Roles of guanine nucleotides and P2-purinergic agonists 总被引:20,自引:0,他引:20
Release of P-choline and choline from purified rat plasma membrane preparations was increased by GTP and its less hydrolyzable analogues, whereas other nucleotide triphosphates had little or no effect. Stimulation by guanosine 5'-(3-O-thiol)triphosphate (GTP gamma S) was dependent upon magnesium, inhibited by guanosine 5'-(2-O-thiol)diphosphate, and independent of calcium. ATP and ADP (1-100 microM) markedly enhanced the GTP gamma S stimulation of P-choline plus choline release but had no effect alone. ADP was as effective as ATP and nonhydrolyzable ATP analogues produced a similar or greater stimulation, whereas AMP and adenosine were much less effective. Vasopressin (0.1 microM) also produced a small stimulation. Under conditions in which protein kinase C was activated, PMA also stimulated the response to GTP gamma S but was ineffective in its absence. P-choline was the initial product which was hydrolyzed to choline. Guanine nucleotide and purinergic effects were also apparent on phosphatidylcholine degradation. EGTA, at 0.5 mM, completely removed purinergic stimulation but did not affect P-choline plus choline released in response to GTP gamma S alone. Prior treatment of plasma membranes with cholera toxin or prior injection of animals with islet-activating protein did not affect the stimulation of P-choline plus choline release either by GTP gamma S alone or by GTP gamma S plus ATP. These results indicate that a phosphatidylcholine phospholipase C is coupled to purinergic receptors in rat liver plasma membranes by a GTP-binding protein. Hydrolysis of phosphatidylcholine could contribute to hepatic diacylglycerol levels and thus influence protein kinase C activity. 相似文献
10.
Biochemical similarity among serologically distinct flagellins of Campylobacter jejuni 总被引:1,自引:0,他引:1
Irving Nachamkin Ruth-Hogue Angeletti Michael B. Prystowsky 《FEMS microbiology letters》1988,51(2-3):149-152
Abstract We describe a simplified method for obtaining highly purified flagellin, suitable for biochemical analysis using HPLC-gel permeation. Amino acid composition and N-terminal sequence analyses were performed on flagellins from serologically distinct isolates. The amino acid composition of flagellin from 10 strains was very similar. The N-terminal amino acid sequence is highly conserved. Significant sequence homology was found with flagellin of Bacillus subtilis . 相似文献