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51.
Interaction of sulfate assimilation with carbon and nitrogen metabolism in Lemna minor 总被引:5,自引:0,他引:5
Kopriva S Suter M von Ballmoos P Hesse H Krähenbühl U Rennenberg H Brunold C 《Plant physiology》2002,130(3):1406-1413
Cysteine synthesis from sulfide and O-acetyl-L-serine (OAS) is a reaction interconnecting sulfate, nitrogen, and carbon assimilation. Using Lemna minor, we analyzed the effects of omission of CO(2) from the atmosphere and simultaneous application of alternative carbon sources on adenosine 5'-phosphosulfate reductase (APR) and nitrate reductase (NR), the key enzymes of sulfate and nitrate assimilation, respectively. Incubation in air without CO(2) led to severe decrease in APR and NR activities and mRNA levels, but ribulose-1,5-bisphosphate carboxylase/oxygenase was not considerably affected. Simultaneous addition of sucrose (Suc) prevented the reduction in enzyme activities, but not in mRNA levels. OAS, a known regulator of sulfate assimilation, could also attenuate the effect of missing CO(2) on APR, but did not affect NR. When the plants were subjected to normal air after a 24-h pretreatment in air without CO(2), APR and NR activities and mRNA levels recovered within the next 24 h. The addition of Suc and glucose in air without CO(2) also recovered both enzyme activities, with OAS again influenced only APR. (35)SO(4)(2-) feeding showed that treatment in air without CO(2) severely inhibited sulfate uptake and the flux through sulfate assimilation. After a resupply of normal air or the addition of Suc, incorporation of (35)S into proteins and glutathione greatly increased. OAS treatment resulted in high labeling of cysteine; the incorporation of (35)S in proteins and glutathione was much less increased compared with treatment with normal air or Suc. These results corroborate the tight interconnection of sulfate, nitrate, and carbon assimilation. 相似文献
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In addition to protein identification, characterization of post-translational modifications (PTMs) is an essential task in proteomics. PTMs represent the major reason for the variety of protein isoforms and they can influence protein structure and function. Upon matrix-assisted laser desorption/ionization (MALDI) most post-translationally modified peptides form a fraction of labile molecular ions, which lose PTM-specific residues only after acceleration. Compared to fully accelerated ions these fragment ions are defocused and show in reflector mass spectra reduced resolution. A short time Fourier transform using a Hanning window function now uses this difference in resolution to detect the metastable fragments. Its application over the whole mass range yields frequency distributions and amplitudes as a function of mass, where an increased low frequency proportion is highly indicative for metastable fragments. Applications on the detection of metastable losses originating from carboxamidomethylated cysteines, oxidized methionines, phosphorylated and glycosylated amino acid residues are presented. The metastable loss of mercaptoacetamide detected with this procedure represents a new feature and its integration in search algorithms will improve the specificity of MALDI peptide mass fingerprinting. 相似文献
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Reynald Olivier Urs Scherrer Jean-Daniel Horisberger Bernard C Rossier Edith Hummler 《Journal of applied physiology》2002,93(5):1881-1887
The amiloride-sensitive epithelial Na(+) channel (ENaC) is essential for fluid clearance from the airways. An experimental animal model with a reduced expression of ENaC, the alpha-ENaC transgenic rescue mouse, is prone to develop edema under hypoxia exposure. This strongly suggests an involvement of ENaC in the pathogenesis of pulmonary edema. To investigate the pathogenesis of this type of edema, primary cultures of tracheal cells from these mice were studied in vitro. An ~60% reduction in baseline amiloride-sensitive Na(+) transport was observed, but the pharmacological characteristics and physiological regulation of the channel were similar to those observed in cells from wild-type mice. Aprotinin, an inhibitor of serine proteases, blocked 50-60% of the basal transepithelial current, hypoxia induced downregulation of Na(+) transport, and beta-adrenergic stimulation was effective to stimulate Na(+) transport after the hypoxia-induced decrease. When downregulation of ENaC activity (such as observed under hypoxia) is added to a low "constitutive" ENaC expression, the resulting reduced Na(+) transport rate may be insufficient for airway fluid clearance and favor pulmonary edema. 相似文献
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Some misprints appeared on page 640, in Table II and in the last paragraph of Section 2.2 (line 9). One should read: "3.075 × 10-2", "-4.900 × 10-4", "1.440 × 10-5", "2.500 × 10-9" and "1.0 × 10-8", respectively (there are not exponential functions). 相似文献
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The case of a boy with Prader-Willi syndrome (PWS) who suffered from respiratory problems since birth and suddenly died at the age of 6.5 years, 4 months after initiation of GH therapy, is presented. This case indicates the possibility of fatal courses in infants and children with PWS as a consequence of respiratory problems and raises the question as to a causal connection between the initiation of GH therapy and the sudden death of this child. 相似文献
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