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1.
Phosphorylation of lens membranes with a cyclic AMP-dependent protein kinase purified from the bovine lens 总被引:1,自引:0,他引:1
We report the phosphorylation of lens membranes with a cAMP-dependent protein kinase isolated from bovine lenses. The holoenzyme was eluted from DEAE agarose at less than 100 mM NaCl and from gel filtration columns with a relative molecular weight of 180 000. The regulatory subunit was identified with the affinity label 8-azido-[32P]cAMP. Four focusing variants with relative molecular weights of 49 000 were seen on two-dimensional gels. The catalytic subunit was purified approx. 5000-fold and migrated at 42 000 Mr on SDS gels. Based on these observations, the enzyme is classified as a Type I cAMP-dependent protein kinase. Purified lens plasma membranes were incubated with the holoenzyme or its catalytic subunit in the presence of 32P-labeled ATP. Several membrane proteins, including the major lens membrane polypeptide, MP26, were shown to be substrates for the kinase in this reaction. MP26 appears to be the major component of intercellular junctions in the lens. Studies with protease treatments on labeled membranes appeared to localize the phosphorylation sites to the cytoplasmic side of the membrane. 相似文献
2.
Teresa K. Aman Bruce A. Maki Thomas J. Ruffino Eileen M. Kasperek Gabriela K. Popescu 《The Journal of biological chemistry》2014,289(27):18805-18817
Protein kinase A (PKA) enhances synaptic plasticity in the central nervous system by increasing NMDA receptor current amplitude and Ca2+ flux in an isoform-dependent yet poorly understood manner. PKA phosphorylates multiple residues on GluN1, GluN2A, and GluN2B subunits in vivo, but the functional significance of this multiplicity is unknown. We examined gating and permeation properties of recombinant NMDA receptor isoforms and of receptors with altered C-terminal domain (CTDs) prior to and after pharmacological inhibition of PKA. We found that PKA inhibition decreased GluN1/GluN2B but not GluN1/GluN2A gating; this effect was due to slower rates for receptor activation and resensitization and was mediated exclusively by the GluN2B CTD. In contrast, PKA inhibition reduced NMDA receptor-relative Ca2+ permeability (PCa/PNa) regardless of the GluN2 isoform and required the GluN1 CTD; this effect was due primarily to decreased unitary Ca2+ conductance, because neither Na+ conductance nor Ca2+-dependent block was altered substantially. Finally, we show that both the gating and permeation effects can be reproduced by changing the phosphorylation state of a single residue: GluN2B Ser-1166 and GluN1 Ser-897, respectively. We conclude that PKA effects on NMDA receptor gating and Ca2+ permeability rely on distinct phosphorylation sites located on the CTD of GluN2B and GluN1 subunits. This separate control of NMDA receptor properties by PKA may account for the specific effects of PKA on plasticity during synaptic development and may lead to drugs targeted to alter NMDA receptor gating or Ca2+ permeability. 相似文献
3.
Anton Pauw Sunshine A. Van Bael Halton A. Peters Steven D. Allison José L. C. Camargo Miguel Cifuentes-Jara Aurlstela Conserva Teresa Garcia Restom Tamara Heartsill-Scalley Scott A. Mangan Gabriela Nunez-lturri Elsie Rivera-Ocasio Mark Rountree Susanne Vetter Carolina Volkmer de Castllho 《Biotropica》2004,36(3):410-413
4.
Gabriela VizÁrovÁ 《Biologia Plantarum》1987,29(3):230-233
The cultivars of barley and wheat resistant to mildew had a higher level of free zeatin and its derivatives during the whole
ontogeny than the susceptible cultivars. The effect of exogenous application of cytokinins on the growth ofErysiphe graminis DC. was different. Kinetin and benzylaminopurine showed only a slight inhibitory effect. Zeatin and its derivatives completely
inhibited growth of this fungus.
Presented at the International Symposium “Plant Growth Regulators” held on June 18-22 1984 at Liblice, Czechoslovakia. 相似文献
5.
Aleš Vančura Ivana Vančurová Jan Kopecký Jaroslav Maršálek Daniel Cikánek Gabriela Basařová Vladimir Křišťan 《Archives of microbiology》1989,151(6):537-540
Synthesis of threonine dehydratase in Streptomyces fradiae was positively influenced by valine and negatively by isoleucine. However, these two amino acids had no effect on the activity of this enzyme. Synthesis of threonine dehydratase in -aminobutyrate resistant mutants of S. fradiae was pronouncedly less sensitive to the positive effect of valine and this change in regulation led to valine overproduction. Synthesis of acetohydroxy acid synthase is regulated in a similar manner to that of threonine dehydratase, however a lower level of expression was detected in -aminobutyrate resistant mutants. And again, no effect of branched-chain amino acids on acetohydroxy acid synthase activity was observed. It follows that in S. fradiae synthesis of threonine dehydratase is the main regulatory mechanism governing production and the mutual ratio of synthesized valine and isoleucine.Abbreviations -AB
-aminobutyrate
- AHAS
acetohydroxy acid synthase
- -KB
-ketobutyrate
- MNNG
N-methyl-N-nitro-N-nitrosoguanidine
- TD
threonine dehydratase
- Trans. B.
transaminase of branched-chain amino acids
- VDH
valine dehydrogenase 相似文献
6.
Daniel Wolff Mitzy Canessa-Fischer Fernando Vargas Gabriela Díaz 《The Journal of membrane biology》1971,6(4):289-303
Summary The lipid content and composition from an axolemma-rich preparation isolated from squid retinal axons was analyzed.The lipids, which accounted for 45.5% of the dry weight of this membrane, were composed of 22% cholesterol, 66.7% phospholipids and 5.2% free fatty acids. The negatively charged species phosphatidyl ethanolamine (37%), phosphatidyl serine (10%) and lysophosphatidyl ethanolamine (4%) made up 51% of the phospholipids. The amphoteric phosphatidyl choline and sphingomyelin accounted for 39% and 4%, respectively.The relative distribution of fatty acids in each of the isolated phospholipids was studied. The most remarkable feature of these phospholipids was the large proportion of long-chain polyunsaturated fatty acids. The 226 acyl chain accounted for 37% in phosphatidyl ethanolamine, 21.7% in phosphatidyl choline, 17.5% on phosphatidyl serine and 20.3% in sphingomyelin (all expressed as area %).The molar fraction of unsaturated fatty acids reached 65% in phosphatidyl ethanolamine and 42.0 and 44.8% in phosphatidyl choline and phosphatidyl serine, respectively. The double bond index in these species varied between 1.0 and 2.6.The lipid composition of the axolemma-rich preparation isolated from squid retinal axons appears to be similar to other excitable plasma membranes in two important features: (a) a low cholesterol/phospholipid molar ratio of 0.61; and (b) the polyunsaturated nature of the fatty acid of their phospholipids.This particular chemical composition may contribute a great deal to the molecular unstability of excitable membranes.The preceding papers of this series were published inArchives of Biochemistry and Biophysics. 相似文献
7.
Time courses of formation of inositol 1,4,5-trisphosphate (IP3 ) were followed in the leaves of non-acclimated and cold (2°C)-acclimated winter oilseed rape ( Brassica napus L. var. oleifera ) plants, subjected to different freezing temperatures or to polyethylene glycol 8000 (PEG) and abscisic acid (ABA) treatments. Changes in water potential (Ψw ) and in ABA level in the frost- and PEG-treated tissues were also determined. Results obtained indicate that temperatures sligthly higher than LT50 induced a transient and substantial increase in IP3 level, both in non-acclimated and cold-acclimated tissues. At comparable freezing temperature (–5°C) the response of cold-acclimated leaves was lower than that of non-acclimated ones. The PEG-depedent decrease in Ψw to –0.9 MPa or ABA (0.1 m M ) treatment gave rise to a transient increase in IP3 content in non-acclimated tissues only. Collectively, the data indicate that cold acclimation of plants may lead to lower cell responsiveness to the factors studied in terms of induction of IP3 formation. Changes in the IP3 content, observed in the present experiments, support our previous suggestion that non-killing freezing temperatures may induce the phosphoinositide pathway, both in non-acclimated and cold-acclimated tissues. Lowering of tissue water potential to some threshold value or a high exogenous ABA supply may mimic the freezing-dependent reaction in the non-acclimated leaves. 相似文献
8.
Measurement of vitellogenin,a biomarker for exposure to oestrogenic chemicals,in a wide variety of cyprinid fish 总被引:8,自引:0,他引:8
C. R. Tyler B. van der Eerden S. Jobling G. Panter J. P. Sumpter 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(7):418-426
There is increasing concern about man-made chemicals in the aquatic environment that mimic oestrogens because they may disrupt
reproductive function. Vitellogenin, a precursor of egg-yolk in fish and other oviparous animals, may be used as a biomarker
for “oestrogen” exposure. This study investigated the use of a radioimmunoassay developed to carp (Cyprinus carpio) vitellogenin to measure vitellogenin in other species of fish, especially cyprinids that would be of value for field and
laboratory studies on oestrogenic xenobiotics. Of the nine families of fish studied, only vitellogenin from cyprinids (to
which the carp belongs) showed good cross-reactivity in the carp vitellogenin radioimmunoassay. Vitellogenin from cyprinids
native to Europe that cross reacted in the carp vitellogenin radioimmunoassay included: bream (Abramis brama), roach (Rutilus rutilus), rudd (Scardinius erythropthalmus), gudgeon (Gobio gobio) and minnow (Phoxinus phoxinus). Vitellogenin from cyprinids used widely in ecotoxicology that cross reacted in the carp vitellogenin radioimmunoassay included:
fathead minnow (Pimephales promelas), zebrafish (Brachydanio rerio) and goldfish (Carassius auratus). In the cyprinids studies, the concentrations of vitellogenin in mature females were between a few hundred and a thousand
microgram per millilitre. Concentrations of plasma vitellogenin in immature females were always greater than 200 ng·m-1, whereas in males (with the exception of the fathead minnow) plasma vitellogenin concentrations were less than 20 ng·ml-1 (and generally, much lower). The results suggest that the structure of vitellogenin is highly conserved within the cyprinid
family and that the carp vitellogenin radioimmunoassay may be used to measure the concentrations of vitellogenin in plasma
from a wide variety of cyprinids. 相似文献
9.
Ana M. Celentano Gabriela Gorelik María E. Solana Leonor Sterin-Borda Enri Borda Stella M. Gonzlez Cappa 《Prostaglandins & other lipid mediators》1995,49(3)
PGE2 involvement in experimental Trypanosoma cruzi infection depends on the lethal capacity of the parasite subpopulation used. Mice acutely infected with non-lethal K98 displayed an enhancement in PGE2 serum levels during the acute period, while those infected with lethal T. cruzi subpopulations (RA or K98-2) showed levels not different from normal mice. The enhancement detected in K98 group could be related both to an increased number of CD8+ T cell number and to enhanced PGE2 release per cell by CD8+; values of PGE2 release by adherent cells were not altered in this group. Treatment with cyclooxygenase inhibitors enhanced mortality rates of mice infected with K98, and administration of 16,16-dimethyl PGE2 (dPGE) reversed this effect. However, mice infected with RA did not reduce their mortality rates by administration of diverse doses of dPGE. These findings suggest that PGE2 could play a role in resistance in mice infected with K98. 相似文献
10.
Gabriela Sánchez-Mejorada Horacio Merchant-Larios Francisco Alonso-deFlorida Luis B. Morales 《Bulletin of mathematical biology》1994,56(1):147-160
Are there enough mast cells in denervated skeletal muscle to account for autopharmacological mediation of the antigen potentials (APs) elicited by microtaps? Through rough qualitative estimations, some authors have suggested a positive answer to this question. However, in view of measurements performed in this investigation of both the density of mast cells and the diffusion coefficient of antigens, the probability of such mediated effects was found to be relatively low:P=0.016 for egg albumin andP=0.004 for ferritin. Therefore, most APs induced by microtaps should be attributed to the direct effect of antigen over the sensitized muscle fibers. Yet, both the density of mast cells found in this work and the known amount of histamine they are capable of releasing when challenged with antigen, support the hypothesis regarding the involvement of these cells when antigen is massively superfused so as to induce Schultz-Dale reactions in muscle strips. Under this circumstance, the direct and mediated mechanisms may coexist. 相似文献