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Actin based processes that could determine the cytoplasmic architecture of plant cells 总被引:1,自引:0,他引:1
Actin polymerisation can generate forces that are necessary for cell movement, such as the propulsion of a class of bacteria, including Listeria, and the protrusion of migrating animal cells. Force generation by the actin cytoskeleton in plant cells has not been studied. One process in plant cells that is likely to depend on actin-based force generation is the organisation of the cytoplasm. We compare the function of actin binding proteins of three well-studied mammalian models that depend on actin-based force generation with the function of their homologues in plants. We predict the possible role of these proteins, and thus the role of actin-based force generation, in the production of cytoplasmic organisation in plant cells. 相似文献
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Jon S.B. de Vlieger Ard J. Kolkman Kirsten A.M. Ampt Jan N.M. Commandeur Nico P.E. Vermeulen Jeroen Kool Sybren S. Wijmenga Wilfried M.A. Niessen Hubertus Irth Maarten Honing 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2010,878(7-8):667-674
This paper describes the determination and identification of active and inactive estrogenic compounds produced by biosynthetic methods. A hyphenated screening assay towards the human estrogen receptor ligand binding domain (hER)α and hERβ integrating target–ligand interactions and liquid chromatography–high resolution mass spectrometry was used. With this approach, information on both biologic activity and structure identity of compounds produced by bacterial mutants of cytochrome P450s was obtained in parallel. Initial structure identification was achieved by high resolution MS/MS, while for full structure determination, P450 incubations were scaled up and the produced entities were purified using preparative liquid chromatography with automated fraction collection. NMR spectroscopy was performed on all fractions for 3D structure analysis; this included 1D-1H, 2D-COSY, 2D-NOESY, and 1H-13C-HSQC experiments. This multidimensional screening approach enabled the detection of low abundant biotransformation products which were not suitable for detection in either one of its single components. In total, the analytical scale biosynthesis produced over 85 compounds from 6 different starting templates. Inter- and intra-day variation of the biochemical signals in the dual receptor affinity detection system was less than 5%. The multi-target screening approach combined with full structure characterization based on high resolution MS(/MS) and NMR spectroscopy demonstrated in this paper can generally be applied to e.g. metabolism studies and compound-library screening. 相似文献
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Wielinga PY Wachters-Hagedoorn RE Bouter B van Dijk TH Stellaard F Nieuwenhuizen AG Verkade HJ Scheurink AJ 《American journal of physiology. Gastrointestinal and liver physiology》2005,288(6):G1144-G1149
In this study, we investigated in rats if hydroxycitric acid (HCA) reduces the postprandial glucose response by affecting gastric emptying or intestinal glucose absorption. We compared the effect of regulator HCA (310 mg/kg) and vehicle (control) on the glucose response after an intragastric or intraduodenal glucose load to investigate the role of altered gastric emptying. Steele's one-compartment model was used to investigate the effect of HCA on systemic glucose appearance after an intraduodenal glucose load, using [U-(13)C]-labeled glucose and d-[6,6-(2)H(2)]-labeled glucose. Because an effect on postabsorptive glucose clearance could not be excluded, the effect of HCA on the appearance of enterally administered glucose in small intestinal tissue, liver, and portal and systemic circulation was determined by [U-(14)C]glucose infusion. Data show that HCA treatment delays the intestinal absorption of enterally administered glucose at the level of the small intestinal mucosa in rats. HCA strongly attenuated postprandial blood glucose levels after both intragastric (P < 0.01) and intraduodenal (P < 0.001) glucose administration, excluding a major effect of HCA on gastric emptying. HCA delayed the systemic appearance of exogenous glucose but did not affect the total fraction of glucose absorbed over the study period of 150 min. HCA treatment decreased concentrations of [U-(14)C]glucose in small intestinal tissue at 15 min after [U-(14)C]glucose administration (P < 0.05), in accordance with the concept that HCA delays the enteral absorption of glucose. These data support a possible role for HCA as food supplement in lowering postprandial glucose profiles. 相似文献
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Werner A Havinga R Bos T Bloks VW Kuipers F Verkade HJ 《American journal of physiology. Gastrointestinal and liver physiology》2005,288(6):G1150-G1158
Essential fatty acid (EFA) deficiency in mice decreases plasma triglyceride (TG) concentrations and increases hepatic TG content. We evaluated in vivo and in vitro whether decreased hepatic secretion of TG-rich very low-density lipoprotein (VLDL) contributes to this consequence of EFA deficiency. EFA deficiency was induced in mice by feeding an EFA-deficient (EFAD) diet for 8 wk. Hepatic VLDL secretion was quantified in fasted EFAD and EFA-sufficient (EFAS) mice using the Triton WR-1339 method. In cultured hepatocytes from EFAD and EFAS mice, VLDL secretion into medium was measured by quantifying [(3)H]-labeled glycerol incorporation into TG and phospholipids. Hepatic expression of genes involved in VLDL synthesis and clearance was measured, as were plasma activities of lipolytic enzymes. TG secretion rates were quantitatively similar in EFAD and EFAS mice in vivo and in primary hepatocytes from EFAD and EFAS mice in vitro. However, EFA deficiency increased the size of secreted VLDL particles, as determined by calculation of particle diameter, particle sizing by light scattering, and evaluation of the TG-to-apoB ratio. EFA deficiency did not inhibit hepatic lipase and lipoprotein lipase activities in plasma, but increased hepatic mRNA levels of apoAV and apoCII, both involved in control of lipolytic degradation of TG-rich lipoproteins. EFA deficiency does not affect hepatic TG secretion rate in mice, but increases the size of secreted VLDL particles. Present data suggest that hypotriglyceridemia during EFA deficiency is related to enhanced clearance of altered VLDL particles. 相似文献
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Eduardo Vottero Vanina Rea Jeroen Lastdrager Maarten Honing Nico P. E. Vermeulen Jan N. M. Commandeur 《Journal of biological inorganic chemistry》2011,16(6):899-912
CYP102A1, originating from Bacillus megaterium, is a highly active enzyme which has attracted much attention because of its potential applicability as a biocatalyst for
oxidative reactions. Previously we developed drug-metabolizing mutant CYP102A1 M11 by a combination of site-directed and random
mutagenesis. CYP102A1 M11 contains eight mutations, when compared with wild-type CYP102A1, and is able to produce human-relevant
metabolites of several pharmaceuticals. In this study, active-site residue 87 of drug-metabolizing mutant CYP102A1 M11 was
mutated to all possible natural amino acids to investigate its role in substrate selectivity and regioselectivity. With alkoxyresorufins
as substrates, large differences in substrate selectivities and coupling efficiencies were found, dependent on the nature
of residue 87. For all combinations of alkoxyresorufins and mutants, extremely fast rates of NADPH oxidation were observed
(up to 6,000 min−1). However, the coupling efficiencies were extremely low: even for the substrates showing the highest rates of O-dealkylation,
coupling efficiencies were lower than 1%. With testosterone as the substrate, all mutants were able to produce three hydroxytestosterone
metabolites, although with different activities and with remarkably different product ratios. The results show that the nature
of the amino acid at position 87 has a strong effect on activity and regioselectivity in the drug-metabolizing mutant CYP102A1
M11. Because of the wide substrate selectivity of CYP102A1 M11 when compared with wild-type CYP102A1, this panel of mutants
will be useful both as biocatalysts for metabolite production and as model proteins for mechanistic studies on the function
of P450s in general. 相似文献