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61.
Guadalupe Albarrán Kenneth E. Collins Carol H. Collins 《Journal of molecular evolution》1987,25(1):12-14
Summary Calcium carbonate labeled with carbon-14 was self-irradiated by means of the -decay of its carbon-14. A number of products containing one or two carbon atoms were identified by high performance liquid chromatography. Formic and oxalic acids were produced in relatively high yields, while glyoxylic, glycolic, and acetic acids, as well as formaldehyde and methanol, were formed in lower yields. These results support the suggestion that carbonates subjected to ionizing radiation could have been a source of carbon for organic synthesis on the primitive earth. 相似文献
62.
Neha Abrol Nikolai Smolin Gareth Armanious Delaine K. Ceholski Catharine A. Trieber Howard S. Young Seth L. Robia 《The Journal of biological chemistry》2014,289(37):25855-25866
To determine the structural and regulatory role of the C-terminal residues of phospholamban (PLB) in the membranes of living cells, we fused fluorescent protein tags to PLB and sarco/endoplasmic reticulum calcium ATPase (SERCA). Alanine substitution of PLB C-terminal residues significantly altered fluorescence resonance energy transfer (FRET) from PLB to PLB and SERCA to PLB, suggesting a change in quaternary conformation of PLB pentamer and SERCA-PLB regulatory complex. Val to Ala substitution at position 49 (V49A) had particularly large effects on PLB pentamer structure and PLB-SERCA regulatory complex conformation, increasing and decreasing probe separation distance, respectively. We also quantified a decrease in oligomerization affinity, an increase in binding affinity of V49A-PLB for SERCA, and a gain of inhibitory function as quantified by calcium-dependent ATPase activity. Notably, deletion of only a few C-terminal residues resulted in significant loss of PLB membrane anchoring and mislocalization to the cytoplasm and nucleus. C-terminal truncations also resulted in progressive loss of PLB-PLB FRET due to a decrease in the apparent affinity of PLB oligomerization. We quantified a similar decrease in the binding affinity of truncated PLB for SERCA and loss of inhibitory potency. However, despite decreased SERCA-PLB binding, intermolecular FRET for Val49-stop (V49X) truncation mutant was paradoxically increased as a result of an 11.3-Å decrease in the distance between donor and acceptor fluorophores. We conclude that PLB C-terminal residues are critical for localization, oligomerization, and regulatory function. In particular, the PLB C terminus is an important determinant of the quaternary structure of the SERCA regulatory complex. 相似文献
63.
Proteome analysis of rat liver mitochondria reveals a possible compensatory response to endotoxic shock 总被引:2,自引:0,他引:2
Miller I Gemeiner M Gesslbauer B Kungl A Piskernik C Haindl S Nürnberger S Bahrami S Redl H Kozlov AV 《FEBS letters》2006,580(5):1257-1262
Organ failure induced by endotoxic shock has recently been associated with affected mitochondrial function. In this study, effects of in vivo lipopolysaccharide-challenge on protein patterns of rat liver mitochondria in treated animals versus controls were studied by two-dimensional electrophoresis (differential image gel electrophoresis). Significant upregulation was found for ATP-synthase alpha chain and superoxide dismutase [Mn]. Our data suggest that endotoxic shock mediated changes in the mitochondrial proteome contribute to a compensatory reaction (adaptation to endotoxic shock) rather than to a mechanism of cell damage. 相似文献
64.
65.
Abstract: The effect of phloretin on prostaglandin (PG) F2α -induced phosphoinositide hydrolysis and elevation of intracellular Ca2+ concentration was examined in cultured rat astrocytes. Phloretin inhibited PGF2α (1 μ M )-induced phosphoinositide hydrolysis in a concentration-dependent manner with an IC50 value of 16 μ M . The inhibitory action of phloretin was specific for PGs. The addition of increasing concentrations of phloretin caused progressive shifts of the dose-response curves of PGF2α to the right. In digitoninpermeabilized astrocytes, phloretin (100 μ M ) inhibited the stimulation induced by PGF2α (1 μ M ) plus GTPγS (50 μ M ) without affecting that induced by GTPγS alone. PGF2α at 1 μ M transiently increased astrocytic intracellular Ca2+ concentration in 39% of the cells tested. The response was completely blocked by 100 μ M phloretin and the calcium response recovered again after washing out phloretin. These results suggest that phloretin is an antagonist of PGF2α receptor linked to phospholipase C in astrocytes. 相似文献
66.
Calcium/Calmodulin-Stimulated Protein Kinase II Is Present in Primary Cultures of Cerebral Endothelial Cells 总被引:1,自引:0,他引:1
Mária A. Deli Ferenc Joó István Krizbai Imre Lengyel Maria G. Nunzi Joachim R. Wolff† 《Journal of neurochemistry》1993,60(5):1960-1963
Abstract: Calcium/calmodulin-stimulated protein kinase II (CaMPK II). a major kinase in brain, has been established to play an important role in neurotransmitter release and organization of postsynaptic receptors, and it is known to be involved in long-term potentiation and memory. Less is known about the function of this enzyme in nonneural cells. Here we report on the production, presence, and phosphorylation of the α-subunit of CaM-PK II in primary cultures of cerebral endothelial cells. These results raise the possibility that α-CaM-PK II can act as one of the key enzymes of calcium-mediated intracellular signaling in the cerebral endothelial cells and suggest that α-CaM-PK II may participate in such basic cellular processes as permeability in physiological and pathological conditions. 相似文献
67.
68.
Kowal D Zhang J Nawoschik S Ochalski R Vlattas A Shan Q Schechter L Dunlop J 《Biochemical and biophysical research communications》2002,294(3):655-659
Using a universal signaling assay employing G-protein chimeras comprising the C-terminal five amino acids of Gi1/2, Gi3, Go, and Gz fused to Gq, the calcium mobilizing G-protein, we explored the role of the C-terminus of Gi family G-proteins as a determinant for 5-HT(1A) receptor functional coupling. Co-expression of the 5-HT(1A) receptor with each of the Gq/Gi family chimeras resulted in a concentration-dependent increase in calcium upon addition of 5-HT, although the coupling efficiency differed dramatically. Gq/Gi3 resulted in the most efficient coupling based on both potency and relative maximum response to 5-HT. Gq/Go also produced efficient coupling in terms of relative 5-HT efficacy (76% of the Gq/Gi3 maximum response), although 5-HT exhibited 4-fold lower agonist potency, and Gq/Gz and Gq/Gi1/2 conferred poor functional coupling. Agonist potencies and relative efficacies determined for a number of 5-HT(1A) receptor agonists using Gq/Gi3 coupling were significantly weaker than those described previously for coupling through the native G-protein. These results indicate the C-terminus of Gi3 as an important determinant for coupling to the 5-HT(1A) receptor, while the reduced functional agonist activities suggest additional motifs participate in receptor/G-protein coupling. 相似文献
69.
O'Neill AF Hagar RE Zipfel WR Nathanson MH Ehrlich BE 《Biochemical and biophysical research communications》2002,294(3):719-725
It has been proposed that the inositol 1,4,5-trisphosphate receptor (InsP(3)R) type III acts as a trigger for InsP(3)-mediated calcium (Ca(2+)) signaling, because this InsP(3) isoform lacks feedback inhibition by cytosolic Ca(2+). We tested this hypothesis in RIN-m5F cells, which express predominantly the type III receptor. Extracellular ATP increases Ca(2+) in these cells, and we found that this effect is independent of extracellular Ca(2+) but is blocked by the InsP(3)R antagonist heparin. There was a dose-dependent increase in the number of cells responding to ATP and two-photon flash photolysis of caged-Ca(2+) heightened the sensitivity of RIN-m5F cells to this increase. These findings provide evidence that Ca(2+) increases the sensitivity of the InsP(3)R type III in intact cells and supports the idea that this isoform can act as a trigger for hormone-induced Ca(2+) signaling. 相似文献
70.
In a screen for calcium-regulated gene expression during growth and development ofDictyostelium discoideum we have identified an asparaginyl tRNA synthetase (ddAsnRS) gene, the second tRNA synthetase gene identified in this organism. TheddAsnRS gene shows many unique features. One, it is repressed by lowering cellular calcium, making it the first known calcium-regulated
tRNA synthetase. Two, despite the calcium-dependence, its expression is unaltered during the cell cycle, making this the firstD. discoideum gene to show a calcium-dependent but cell cycle phase-independent expression. Finally, the N-terminal domain of the predicted
ddAsnRS protein shows higher sequence similarity to Glutaminyl tRNA synthetases than to other Asn tRNA synthetases. These
unique features of theAsnRS from this primitive eukaryote not only point to a novel mechanism regulating the components of translation machinery and
gene expression by calcium, but also hint at a link between the evolution ofGlnRS andAsnRS in eukaryotes. 相似文献