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11.
The subcellular distribution of Ca2+/calmodulin-stimulated adenylate cyclase activity was studied in comparison with that of guanine nucleotide-stimulated cyclase activity. The distributions of these activities were similar among the crude fractions but differed among the purified subsynaptosomal fractions. The specific activity of Ca2+/calmodulin-stimulated cyclase was highest in a light synaptic membrane fraction, which has few, if any, postsynaptic densities, whereas that of guanine nucleotide-stimulated cyclase was highest in a heavier synaptic membrane fraction rich in postsynaptic densities. These results suggest that the Ca2+/calmodulin-stimulated cyclase has, at least in part, a different cellular or subcellular location than the guanine nucleotide-stimulated cyclase.Abbreviations used CaM
calmodulin
- GppNHp
guanosine 5-(,-imino) triphosphate 相似文献
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The interaction between glucagon and dicaprylphosphatidylcholine (DCPC) was studied by fluorescence, circular dichroism and calorimetry, as well as by 1H- and 31P-nuclear magnetic resonance. The water-soluble lipid-protein complex was also characterized by gel filtration and ultracentrifugation. The complex appeared to be monodisperse by sedimentation equilibrium measurements, with a molecular weight of (4.55 ± 0.57)·104. This complex contained approximately 7 molecules of glucagon and 35 molecules of phospholipid. Proton-decoupled 31P-NMR spectra of the phospholipid in the lipid-protein complex display narrower resonances than those of sonicated vesicles of DCPC, and 1H-31P coupling could be detected in proton coupled spectra. These NMR results, together with gel-filtration results, suggest that glucagon ‘solubilizes’ phospholipid aggregates, forming a lipid-protein complex which is smaller than sonicated preparations of DCPC. 1H-NMR resonance of both the methionine methyl group (met-27) and the aromatic envelope of glucagon are broadened by the phospolipid, indicating that the C-terminal region and the aromatic residues are involved in the interaction with the phospholipid. Nuclear magnetic resonance titrations of the imidazole ring C(2) and C(4) protons of the histidine residue of glucagon show that DCPC lowers the pK of the imidazole. The alterations caused by the phospholipid in the far and near ultraviolet CD spectra of glucagon reflect, respectively, the increased helix content of the hormone and the fact that the aromatic residues are located in a more structured environment. The phospholipid also alters the fluorescence properties of glucagon, shifting the fluorescence emission maximum of the hormone to shorter wavelength, and enhancing its relative intensity. This suggests that the fluorophore is experiencing a more hydrophobic environment in the presence of the lipid. Binding of glucagon to the phospholipid was analysed by Scatchard plots of the enhancement of fluorescence caused by the phospholipid and showed that the equilibrium binding constants of glucagon to DCPC are (4.4 ± 0.5)·104M?1 and (7.5±0.5)·104M?1, at 15°C and 25°C, respectively. The average number of moles of phospholipid bound per mole of glucagon is 4.4±0.6. The isothermal enthalpy of reaction of glucagon with DCPC is ?20.5 kcal/mol of glucagon at 25°C and ?32.5 kcal/mol of glucagon at 15°C. The observed enthalpies can arise from glucagon-induced cyrstallization of the phospholipid, from the non-covalent interactions between the peptide and lipid as well as from the lipid-induced conformational change in the protein. These results demonstrate that, unlike the complexes formed between glucagon and phospholipids which form more stable bilayers, the complex formed between glucagon and DCPC is stable over a wide range of temperatures, including temperatures well above the phase transition. 相似文献
14.
The use of acetylated cytochrome c in detecting superoxide anion production in rabbit alveolar macrophages 总被引:3,自引:0,他引:3
V N Nasrallah P S Shirley Q Myrvik M Waite 《Journal of immunology (Baltimore, Md. : 1950)》1983,131(5):2104-2106
Polymorphonuclear phagocytes have been shown to undergo marked alteration in oxidative metabolism during phagocytosis. These alterations, collectively known as the "respiratory burst", include increased glucose oxidation through the hexose monophosphate shunt (1), increased oxygen consumption (1), and increased superoxide (O-2)3 (2) and H2O2 production (3). Similar metabolic events have also been shown to occur in the rabbit alveolar macrophage (AM). There is consistent evidence that the macrophage undergoes increased oxygen consumption (4-6) and hexose monophosphate shunt activity (4-9) upon phagocytosis. There are conflicting data, however, concerning the ability of the macrophage to produce O-2. Some studies suggest that macrophages are incapable of producing measurable amounts of O-2 upon phagocytosis (7, 10-12). Other studies, however, suggest that macrophages are indeed capable of producing substantial amounts of O-2 during phagocytosis (8, 13-15). This study was designed to resolve the discrepancies in the literature concerning O-2 production in macrophages. 相似文献
15.
James W. Truman Dorothy B. Rountree Shirley E. Reiss Lawrence M. Schwartz 《Journal of insect physiology》1983,29(12):895-900
The relationship between the ecdysteroid titre and eclosion hormone was explored for the pupal and adult ecdyses of Manduca sexta. Ecdysteroid treatment late during either moult caused a dosedependant delay in the time of ecdysis. Sensitivity to exogenous steroid treatment dropped off as the respective moults neared completion and in both cases coincided with the time of the low point in the endogenous ecdysteroid titre. It was concluded that an ecdysteroid decline is a normal prerequisite for the ecdyses of both stages. The steroid drop is important for two aspects of the eclosion hormone system: it causes target tissues to become sensitive to the peptide and it is a prerequisite for the subsequent release of eclosion hormone itself. Thus, the dual action of the declining ecdysteroid titre insures that when eclosion hormone is released, the tissues will be competent to respond to it. 相似文献
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Evaluation of Factors Related to Growth of Rift Valley Fever Virus in Suspended Cell Cultures 总被引:2,自引:2,他引:0 下载免费PDF全文
Jerry S. Walker Richard C. Carter Frederick Klein Shirley E. Snowden Ralph E. Lincoln 《Applied microbiology》1969,17(5):658-664
The effect of several controlled variables on the peak titer and fold increase of Rift Valley fever virus grown in suspension culture on two variants of Earle's L cell, L-DR and L-MA clone 1-1, was studied. No significant amount of cell-associated virus was found at 24 hr, indicating a release of virus soon after its formation. Mild sonic treatment of the virus produced in serum-free medium increased the infective titer about 10x. This difference was not observed with virus produced in medium supplemented with serum. Peak titer was not affected by medium used during the infection period, by multiplicity of inoculum (MOI), or by initial cell concentration within the test range of 10(4) to 2 x 10(6) cell/ml. Cell strain employed influenced titer, because the L-DR cell did not produce virus efficiently at low MOI and low initial cell concentration. The time of peak titer and fold replication was dependent on MOI and initial cell concentration. Differences in virus propagation in monolayer and suspension systems are discussed. 相似文献
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1. A transglucosylase fraction has been obtained from the mycelium of Aspergillus niger. 2. The preparation will transfer alpha-d-glucopyranosyl residues from maltose and other alpha-d-glucopyranosides to phenolic and alcoholic hydroxyl groups and to carboxylic acid groups. 3. alpha-Isomaltosides and alpha-maltosides are formed when resorcinol and catechol are used as acceptors. 4. pH precipitation and DEAE-cellulose chromatography were used to resolve the activity into two fractions. The properties, in particular polyol inhibition, of one of these fractions have been examined in detail. 相似文献