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1.
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
2.
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
3.
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
4.
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
5.
Biosynthesis of chlortetracycline is localized differently under low- and high-production conditions (standard low-production strain and its high-production variant). The experimental evidence was based on the assay of anhydrotetracycline oxygenase in subcellular fractions, ultracytochemical localization and electron-probe X-ray microanalysis of the product in the mycelium. Overproduction of chlortetracycline is closely associated with compartmentation of biosynthetic enzymes and with an efficient export of the antibiotic out of the cell. 相似文献
6.
Twenty-one heifers were synchronized with PGF(2) alpha and 22 heifers were stimulated with FSH-P in decreasing doses and synchronized with PGF(2) alpha. The beginning of LH rise was observed to be 47.6+/-14.0 h and 35.9+/-1.3 h (P < 0.05) and the peak of LH rise was observed at 53.8 +/- 13.4 h and 40.14+/-1.4 h (P < 0.05) after the luteolyticum administration in the synchronized and superovulated group respectively. The beginning of LH rise was observed 6.9+/-6.7 h and 4.8+/-2.6 h (P < 0.05) and the LH peak was observed 11.8+/-7.7 h and 8.3+/-3.2 h (P < 0.05) after the frist symptoms of oestrus in the synchronized and superovulated group respectively. Ovulation was not observed in stimulated heifers in the period of 23-25 h after the preovulatory LH rise. Compact cumulus oophorus was seen at 30.5%, expanded at 67.0 and partial at 2.5% during this interval of 23-25h. Within this same interval 26.9%, 51.3% and 21.8% oocytes without perivitelline space, with perivitelline space and with extruded first polar body were aspirated respectively. It may be concluded from the reported results that to recover fully mature oocytes for in vitro fertilization, it will be necessary to monitor the preovulatory period of the donor cow in great detail. 相似文献
7.
Photobiont cells of the lichen Evernia prunastri have completely been separated from their fungal partner by filtration through a bed of Sepharose 2B. Both mannitol and ribitol have been quantified by gas-liquid chromatography in the different steps of the isolation procedure. Absence of mannitol, which is exclusively produced by the mycobiont, has been used as the best probe to monitor isolation. 相似文献
8.
Invertase immobilization via its carbohydrate moiety 总被引:1,自引:0,他引:1
After periodate oxidation of its glycosidic component, invertase was covalently bound onto three types of modified solid supports: glycidyl methacrylate, styrene-divinylbenzene copolymers, and bead cellulose. Direct reaction of the invertase aldehyde groups that were formed with amino groups of the support and use of the modified Ugi reaction have been employed as immobilization procedures. Apart from binding methods, the important effects of the buffer, support, conditions of periodate oxidation, and the length of the spacer on the activity of the enzyme conjugate have been investigated. Superior conjugate activity was obtained, via modified Ugi reaction, by the immobilization of a suitably oxidized invertase to a styrene-divinylbenzene copolymer having free amino groups. 相似文献
9.
Emilio Román Galán Jaun A. Galbis Pérez Mariá A. Arévalo Arévalo 《Carbohydrate research》1983,116(2):255-262
The reaction between 2-(benzylamino)-2-deoxy-d-glycero-l-gluco-heptose and 5,5-dimethyl-1,3-cyclohexanedione yields 1-benzyl-4,5,6,7-tetrahydro-6,6-dimethyl-2-(d-galacto-pentitol-1-yl)-indol-4-one (2). Acid-catalyzed, intramolecular dehydration of 2 under kinetically controlled conditions gives 1-benzyl-4,5,6,7-tetrahydro-2-α-d-lyxofuranosyl-6,6-dimethylindol-4-one; the anomeric configuration of this compound is only suggested. When the dehydration reaction is conducted under thermodynamically controlled conditions, it produces a 1:1 mixture of the α- and β-d-lyxopyranosyl compounds. The structures of the new compounds were elucidated by chemical and physical methods. 相似文献
10.
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