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排序方式: 共有628条查询结果,搜索用时 218 毫秒
591.
Xiaodan Li Lili Wang X Edward Zhou Jiyuan Ke Parker W de Waal Xin Gu M H Eileen Tan Dongye Wang Donghai Wu H Eric Xu Karsten Melcher 《Cell research》2015,25(1):50-66
AMP-activated protein kinase (AMPK) is a central cellular energy sensor and regulator of energy homeostasis, and a promising drug target for the treatment of diabetes, obesity, and cancer. Here we present low-resolution crystal structures of the human α1β2γ1 holo-AMPK complex bound to its allosteric modulators AMP and the glycogen-mimic cyclodextrin, both in the phosphorylated (4.05 Å) and non-phosphorylated (4.60 Å) state. In addition, we have solved a 2.95 Å structure of the human kinase domain (KD) bound to the adjacent autoinhibitory domain (AID) and have performed extensive biochemical and mutational studies. Together, these studies illustrate an underlying mechanism of allosteric AMPK modulation by AMP and glycogen, whose binding changes the equilibria between alternate AID (AMP) and carbohydrate-binding module (glycogen) interactions. 相似文献
592.
Abstract. The response of the adenylate energy charge (AEC) ratio and the adenine nucleotide pools to nutrients was studied in two perennial marsh plant species. Adenine nucleotide levels and the AEC ratio were measured in Spartina patens (Alton) Muhl. plants which were grown in the greenhouse at various nutrient levels as well as in Spartina alterniflora Loisel. transplants removed from the field but maintained in marsh soil amended with different nutrient supplements. In addition, adenine nucleotide concentrations were measured in both species in their natural environment and compared with that of the same species grown in the greenhouse with a complement of nutrients.
The addition of nutrients stimulated an increase in the individual and total adenylate pools and the AEC ratio. Low nutrient levels resulted in extremely reduced adenylate pools. The AEC ratio was significantly affected in some instances, but did not decrease proportionately with the adenine nucleotide level and was typically maintained at values above 0.60. The adenine nucleotide concentrations measured in the leaves of both species were significantly higher in greenhouse-grown plants compared to field plants, but the AEC ratios were not significantly different.
Because the AEC ratio in plants can be significantly affected by nutrient level. AEC response in field investigations should be planned with attention to the potential effect of dissimilar nutrient levels among study sites. 相似文献
The addition of nutrients stimulated an increase in the individual and total adenylate pools and the AEC ratio. Low nutrient levels resulted in extremely reduced adenylate pools. The AEC ratio was significantly affected in some instances, but did not decrease proportionately with the adenine nucleotide level and was typically maintained at values above 0.60. The adenine nucleotide concentrations measured in the leaves of both species were significantly higher in greenhouse-grown plants compared to field plants, but the AEC ratios were not significantly different.
Because the AEC ratio in plants can be significantly affected by nutrient level. AEC response in field investigations should be planned with attention to the potential effect of dissimilar nutrient levels among study sites. 相似文献
593.
A Lavoinne 《Biochimie》1983,65(1):71-75
1. The digitonin fractionation procedure [Zuurendonk, P. F. and Tager, J. M. (1974) Biochim. Biophys. Acta, 333, 393-399] was used to determine the repartition of adenine nucleotides and inorganic phosphate in isolated hepatocytes from fed and fasted rats. 2. This repartition is not significantly modified in the presence of pyruvate or alanine or lactate + pyruvate for isolated hepatocytes from fasted rats. 3. In isolated hepatocytes from fasted rats, the mitochondrial ATP/ADP X PO4 ratio is two-fold lower than in isolated hepatocytes from fed rats. 4. The cytosolic ATP/ADP X PO4 ratio depends on the nutritional state and (or) on the added substrate for neoglucogenesis. 相似文献
594.
A protein fraction extracted from barley seedlings was shown to bind 3′:5′-cyclic AMP. The binding effect is real and not due to interference with the standard binding-protein assay used. Evidence is presented that this is a specific binding-protein; even at high concentrations other protein fractions from the same source showed no affinity for cyclic AMP. None of a range of cyclic and non-cyclic nucleotides that were examined exhibited a degree of binding with the protein comparable to that with cyclic AMP. The cyclic AMP/binding protein complex has a Kd of 8 nM. This complex eluted at an identical position in the elution sequence from a Sephadex G-150 column as the uncomplexed binding-protein. The barley binding-protein is in a fraction which also exhibits the enzymic activities of glucose 6-phosphatase, ATPase, 5′-nucleotidase, and fructose 1,6-diphosphatase. 相似文献
595.
Sarah McFarlane 《Molecular neurobiology》2000,22(1-3):1-9
Neurons are polarized cells with an axon and a dendritic arbor extending from the soma. Although the molecular mechanisms
underlying axon guidance are rapidly being elucidated, those that regulate the orientation, morphology, and elaboration of
dendritic processes are largely unknown. Several recent papers address these issues, and propose a set of molecular strategies
that control dendrite development. This review discusses these papers and what they reveal to us about how cell signaling
orchestrates neuronal form and connectivity during development. 相似文献
596.
A procedure is described which unequivocally demonstrates the presence of adenosine 3′:5′-cyclic monophosphate in Phaseolus vulgaris. Its concentration was determined spectrophotometrically at 2·6–9·2 nmol g?1 of tissue (dry wt) for 6-day-old seedlings and about one-tenth of this in 13-day-old plants. 相似文献
597.
Abstract: The present study indicates that central 5-hydroxytryptamine (5-HT; serotonin) receptors can be modulated in opposite directions by Ca2+ and guanine nucleotides [guanosine triphosphate (GTP), β, γ-imidoguanosine 5′-triphosphate (GppNHp)]. Thus CaCl2 (≥0.5 mm ) inhibited whereas GTP and GppNHp (10 μm ) stimulated the 5-HT-sensitive adenylate cyclase in the hippocampus of newborn rats. Both the affinity (Kd ?1) and the number (Bmax) of [3H]5-HT binding sites in hippocampal membranes from adult rats were increased in the presence of Ca2+ (≥0.25 mm ); GTP (≥0.1 mm ) and GppNHp (≥0.3; μm ) produced reverse effects. The efficacy of guanine nucleotides in inhibiting specific [3H]5-HT binding was counteracted by Ca2+: the addition of this cation (5mm -CaCl2) to the assay mixture resulted in a 40-fold increase in the IC50 for GTP; the IC50 for GppNHp increased five-fold under the same condition. The examination of the respective effects of Ca2+ and of GTP on the specific binding of [3H]5-HT to various hippocampal membrane preparations (from developing rats, from subcellular fractions of adult tissues, and from adult rats after the selective degeneration of serotoninergic innervation in the forebrain) indicated that the amplitudes of the Ca2+-induced increase and of the GTP-induced decrease were generally correlated. This conclusion did not apply to striatal membranes of kainic acid-treated rats because [3H]5-HT binding sites persisting after the intrastriatal injection of kainic acid (i.e., half of the total number in striatal membranes from control rats) were markedly less affected by GTP but at least as responsive as control membranes to the Ca2+-induced increase. These data are compatible with the hypothesis of a possible coupling of some–but not all–[3H]5-HT binding sites to adenylate cyclase in the rat brain. 相似文献
598.
Treatment of rat thoracic aortic smooth muscle cells (A-10) with sodium fluoride (NaF) resulted in inhibition of β-adrenergic agonist—and forskolin-induced cAMP and ANF-induced cGMP accumulation and stimulation of diacylglycerol (DAG) accumulation. The concentration of NaF and treatment times required to mediate these inhibitory effects were similar to those observed for stimulation of DAG accumulation. Treatment of the cells with NaF also resulted in a loss of [3H]phorbol dibutyrate (PDBu) binding in the cytosolic portion of the cells. In addition, pre-treatment of the cells with NaF resulted in an increase in the adenylate cyclase activity. Pertussis toxin (PT) pre-treatment of the cells did not significantly affect NaF-mediated effects. Pre-treatment of the cells with protein kinase C (PKC) inhibitor staurosporin partially reversed NaF-mediated inhibition of cyclic nucleotides accumulation. These data suggest that inhibition of the formation of agonist-induced cyclic nucleotides by NaF may be due to the formation of DAG and cAMP which lead to the activation of PKC and cAMP-PK, resulting in phosphorylation of key regulatory protein(s) in the cyclic nucleotides pathway. 相似文献
599.
600.
Summary Callus cultures derived from roots of summer squash (Cucurbita pepo L. c.v. Early Prolific Straightneck) grown in the dark at 27° C on Murashige and Skoog medium supplemented per liter with
30 g sucrose, 100 mg myo-inositol, 10 mg indole-butyric acid, 2 mg glycine, 1 mg thiamin, 0.5 mg nicotinic acid, 0.5 mg pyridoxine,
and 2 g Gelrite were capable of synthesizing pyrimidine nucleotides both de novo and through salvage of existing pyrimidine
nucleotides and bases. Evidence that the de novo biosynthesis of pyrimidine nucleotides proceeded via the orotate pathway
in this tissue included: (a) demonstration of the incorporation of NaH14CO3 and [14C6]orotic acid into uridine nucleotides (ΣUMP), and (b) demonstration that the addition of 6-azauridine blocked the incorporation
of these two precursors into ΣUMP.
The synthesis of pyrimidine nucleotides through the salvage of existing pyrimidine bases and ribosides was demonstrated by
measuring the incorporation of [14C2]uracil and [14C2]uridine into ΣUMP. Salvage of both [14C2]uracil and [14C2]uridine was sensitive to inhibition by 6-azauridine or one of its metabolites.
The orotic acid pathway for the de novo biosynthesis of pyrimidine nucleotides was demonstrated to be sensitive to end-product
inhibition. Uridine, or one of its metabolites, inhibited the incorporation of NaH14CO3, but not [14C6]orotic acid, into ΣUMP. Evidence is presented suggesting that Aspartate carbomoyltransferase is the site of feedback control.
This work was supported by the Citrus Research Center and Agricultural Experiment Station of the University of California,
Riverside, CA. Submitted in partial fulfillment of the requirements of the University of California for the Master of Science
degree in botany (F-F.L.) 相似文献