Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A controlled exchange of calcium between the extracellular space (mM Ca2+) and the neuroplasm (microM Ca2+) is considered to be an essential prerequisite for almost every stage of neuronal activity. Our research interest is focused on those compounds, which due to their physico-chemical properties and localization within the synaptic membrane might fulfill the task as neuromodulators for functional synaptic proteins. Because of this specific binding properties towards calcium and their peculiar interactions with calcium in model systems gangliosides (amphiphilic sialic acid containing glycosphingolipids) are favorite candidates for a functional involvement in synaptic transmission of information. In this study we used monolayers to investigate the molecular packing and surface potential at the air/water interface, the interaction of gangliosides with the depsipeptide valinomycin (= monovalent ion carrier), and its influenceability by calcium. Furthermore we looked at calcium effects on the single channel conductance and mean channel life-time of the monovalent ion channel gramicidin A in mixed PC/ganglioside bilayers. In pure ganglioside monolayers the addition of 0.01 mM Ca2+ induces monolayer condensation, a rise in collapse pressure (= higher film stability), a shift of phase transition (= change of conformation), and a more negative head group potential (change of electric properties). In mixed ganglioside-valinomycin monolayers the addition of Ca2+ causes phase separation and/or aggregate formation between the ganglioside and the peptide. Single channel conductance fluctuations as well as mean channel life-time were analyzed for gramicidin A incorporated into binary mixed black lipid membranes of negatively charged gangliosides (GM1, GD1a, GT1b, GMix) and neutral lecithin (DOPC) in different molar ratios. At monovalent electrolyte concentrations up to < 250 mM CsCl the single channel conductance was significantly larger in the negatively charged mixed DOPC/ganglioside membranes than in the neutral DOPC membrane. Additionally, in the presence of gangliosides the mean channel life-time is increased. The addition of calcium (0.05 mM) induced a reduction of single channel conductance of gramicidin A in DOPC- and mixed DOPC/ganglioside membranes. These physico-chemical data in connection with new electromicroscopical evidences for a precise localization of calcium, a calcium pump (Ca(2+)-ATPase), a clustered arrangement of gangliosides in synaptic terminals, and biochemical results with regard to activatory nature of exogenous gangliosides for neuronal protein phosphorylation and ATPases, support the hypothesis of a modulatory function of gangliosides in synaptic transmission.
...
PMID:Calcium-ganglioside interactions and synaptic plasticity: effect of calcium on specific ganglioside/peptide (valinomycin, gramicidin A)-complexes in mixed mono- and bilayers. 128 79

A smooth muscle plasma membrane vesicular fraction (PMV) purified for the (Ca2+/Mg2+)-ATPase has endogenous glycolytic enzyme activity. In the presence of glycolytic substrate (fructose 1,6-diphosphate) and cofactors, PMV produced ATP and lactate and supported calcium uptake. The endogenous glycolytic cascade supports calcium uptake independent of bath [ATP]. A 10-fold dilution of PMV, with the resultant 10-fold dilution of glycolytically produced bath [ATP] did not change glycolytically fueled calcium uptake (nanomoles per milligram protein). Furthermore, the calcium uptake fueled by the endogenous glycolytic cascade persisted in the presence of a hexokinase-based ATP trap which eliminated calcium uptake fueled by exogenously added ATP. Thus, it appears that the endogenous glycolytic cascade fuels calcium uptake in PMV via a membrane-associated pool of ATP and not via an exchange of ATP with the bulk solution. To determine whether ATP produced endogenously was utilized preferentially by the calcium pump, the ATP production rates of the endogenous creatine kinase and pyruvate kinase were matched to that of glycolysis and the calcium uptake fueled by the endogenous sources was compared with that fueled by exogenous ATP added at the same rate. The rate of calcium uptake fueled by endogenous sources of ATP was approximately twice that supported by exogenously added ATP, indicating that the calcium pump preferentially utilizes ATP produced by membrane-bound enzymes.
...
PMID:Comparison of endogenous and exogenous sources of ATP in fueling Ca2+ uptake in smooth muscle plasma membrane vesicles. 131 Oct 20

The stimulation of the purified human erythrocyte calcium pump by acidic phospholipids was investigated using synthetic peptides corresponding to a putative phospholipid-responsive domain [Zvaritch, E., James, P., Vorherr, T., Falchetto, R., Modyanov, N. & Carafoli, E. (1990) Biochemistry 29, 8070-8076] and to the calmodulin-binding domain of the pump. The peptides interfered with the activation of the enzyme by phosphatidylserine and phosphatidic acid in competition assays. The peptide corresponding to the calmodulin-binding domain was found to be the most efficient antagonist. Direct binding measurements using fluorescent derivatives of the peptides confirmed the interaction between the acidic phospholipids and the peptides, and fluorescence titrations of dansylated calmodulin with the purified ATPase showed a direct effect of acidic phospholipids on calmodulin binding. A proteolyzed preparation of the Ca(2+)-ATPase lacking the calmodulin-binding domain confirmed that the phospholipid-induced stimulation is mediated by two sites, one located in the C-terminal portion of the previously identified 44-amino-acid phospholipid-responsive domain, the other in the calmodulin-binding domain.
...
PMID:Identification of two domains which mediate the binding of activating phospholipids to the plasma-membrane Ca2+ pump. 131 84

Ouabainlike factor (OLF) has been extracted from the hypothalamus and adrenals of the ox and rats of the Milan hypertensive strain (MHS) and their normotensive controls (MNS). OLF was identified by its ability to 1) inhibit ouabain-sensitive 86Rb uptake into human erythrocytes, 2) displace [3H]ouabain binding, and 3) inhibit purified dog kidney Na-K-adenosinetriphosphatase (ATPase). Rat and bovine OLF have similar characteristics. Those that are close to ouabain are 1) ligand conditions for maximal inhibitory activity, 2) high-performance liquid chromatography retention time, 3) reversibility of inhibitory activity on Na-K-ATPase, 4) reduced Na-K pump inhibitory activity by K, 5) high affinity for Na-K-ATPase, and 6) no activity on calcium ATPase. OLF does not resemble ouabain in the following characteristics: 1) the capacity of OLF to inhibit ouabain low-affinity Na-K-ATPase isoform is greater than that of ouabain and 2) the capacity of OLF to inhibit renal Na-K-ATPase isoforms is greater when the enzyme is obtained from adult rather than young rats. The yield of OLF is greater from MHS than MNS. These findings represent the first direct evidence that a higher amount of OLF is present in tissues from genetically hypertensive rats than from their inbred normotensive controls, maintained under the same dietary and environmental conditions. This further supports previous observations on the role of OLF in the pathogenesis of MHS hypertension.
...
PMID:Ouabainlike factor in Milan hypertensive rats. 132 60

Myotoxin a, a small basic polypeptide isolated from the venom of prairie rattlesnake (Crotalus viridis viridis), has been shown to bind to sarcoplasmic reticulum (SR) Ca(2+)-ATPase. The attachment of myotoxin a to Ca(2+)-ATPase is believed to cause uncoupling of the calcium pump. In order to further elucidate which portion of myotoxin a is important for the uncoupling action, five peptides were synthesized and two peptide fragments were obtained by chemical cleavage. These peptides correspond to discrete portions of the primary sequence of myotoxin a. The peptides are equivalent to the primary sequence of myotoxin a from 1 to 16 residues, 7 to 22 residues, 13 to 28 residues, 19 to 34 residues, and 25 to 42 residues. Chemically produced fragments are equivalent to 1 to 28 residues and 29 to 42 residues of myotoxin a. Peptides of the sequences "YKQCHKKGGHCFPKEK" and "LGKMDCRWKWKCCKKGSG" of myotoxin a inhibited 45Ca uptake into isolated SR and bound to Ca(2+)-ATPase. The same peptides caused weak skeletal muscle vacuolization similar to that caused by native myotoxin a and increased serum creatine kinase activity. The active peptides correspond to the N-terminal and C-terminal portions of myotoxin a. The inactive or less active peptides have sequences which correspond to the middle sequence of myotoxin a. From this study, both the N-terminal and the C-terminal regions of primary sequence of myotoxin a are required to express myotoxin a's biological activity.
...
PMID:Structure-function relationship of myotoxin a using peptide fragments. 132 55

Affinity-purified polyclonal antibodies, raised against two synthetic peptides corresponding to the R domain and the C terminus of the human cystic fibrosis transmembrane conductance regulator (CFTR), were used to characterize and localize the protein in human epithelial cells. Employing an immunoblotting technique that ensures efficient detection of large hydrophobic proteins, both antibodies recognized and approximately 180-kDa protein in cell lysates and isolated membranes of airway epithelial cells from normal and cystic fibrosis (CF) patients and of T84 colon carcinoma cells. Reactivity with the anti-C terminus antibody, but not with the anti-R domain antibody, was eliminated by limited carboxypeptidase Y digestion. When normal CFTR cDNA was overexpressed via a retroviral vector in CF or normal airway epithelial cells or in mouse fibroblasts, the protein produced had an apparent molecular mass of about 180 kDa. The CFTR expressed in insect (Sf9) cells by a baculovirus vector had a molecular mass of about 140 kDa, probably representing a nonglycosylated form. The CFTR in epithelial cells appears to exist in several forms. N-glycosidase treatment of T84 cell membranes reduces the apparent molecular mass of the major CFTR band from 180 kDa to 140 kDa, but a fraction of the T84 cell CFTR could not be deglycosylated, and the CFTR in airway epithelial cell membranes could not be deglycosylated either. Moreover, wheat germ agglutinin absorbs the majority of the CFTR from detergent-solubilized T84 cell membranes but not from airway cell membranes. The CFTR in all epithelial cell types was found to be an integral membrane protein not solubilized by high salt or lithium diiodosalicylate treatment. Sucrose density gradient fractionation of crude membranes prepared from the airway epithelial cells, previously surface-labeled by enzymatic galactosidation, showed a plasma membrane localization for both the normal CFTR and the CFTR carrying the Phe508 deletion (delta F 508). The CFTR in all cases co-localized with the Na+, K(+)-ATPase and the plasma membrane calcium ATPase, while the endoplasmic reticulum calcium ATPase and mitochondrial membrane markers were enriched at higher sucrose densities. Thus, the CFTR appears to be localized in the plasma membrane both in normal and delta F 508 CF epithelial cells.
...
PMID:Biochemical characterization of the cystic fibrosis transmembrane conductance regulator in normal and cystic fibrosis epithelial cells. 137 Apr 88

In most bacterial cell types studied, low intracellular free calcium is maintained by a variety of secondary exchangers which utilize transmembrane ion gradients. Prokaryotic calcium ATPases appear to be extremely uncommon, and none have been reported in Gram-negative organisms. We demonstrate ATP-dependent calcium uptake in everted membrane vesicles of Flavobacterium odoratum, a common Gram-negative soil and water bacterium. Calcium is transported with an apparent initial rate of 10 nmol/min mg of protein. It is inhibited by 20 microM orthovanadate, a specific P-type ATPase inhibitor, but significantly, it is unaffected by the addition of N-ethylmaleimide, N,N-dicyclohexylcarbodiimide, valinomycin, or nigericin. Because the Ca(2+)-ATPase makes up a high proportion of the total ATPase activity it is easily detected by a soluble ATP hydrolysis assay, with an initial rate for calcium-dependent ATPase activity in vesicles of 25-40 nmol/min.mg at pH 7.8 and 25 degrees C. The calcium-dependent activity is preferentially solubilized by the detergent C12E8 and can be precipitated at 55-80% ammonium sulfate in a fraction free of other contaminating ATPase activities. This partially purified fraction is enriched 15-fold and demonstrates an apparent Km for calcium of 2 microM, and for ATP of 130 microM. The IC50 for vanadate is 1.6 microM. These values are similar to those obtained for the eukaryotic sarcoplasmic reticulum calcium ATPase. The enzyme is rapidly phosphorylated by [gamma-32P]ATP in a calcium-dependent, vanadate-inhibitable manner. The phosphorylated species migrates with an apparent molecular mass of 60 kDa by NaDodSO4-polyacrylamide gel electrophoresis, and the phosphoryl group is sensitive to alkaline conditions, a characteristic of the acylphosphate linkage found in ATPases. These data demonstrate that the majority of calcium transport in F. odoratum is facilitated by a P-type ATPase.
...
PMID:Characterization of a P-type Ca(2+)-ATPase from Flavobacterium odoratum. 138 66

A disruption of calcium homeostasis, leading to a sustained increase in cytosolic calcium levels, has been associated with cytotoxicity in response to a variety of agents in different cell types. We have observed that administration of a single high dose or multiple lower doses of the carcinogenic nephrotoxin ochratoxin A (OTA) to rats resulted in an increase of the renal cortex endoplasmic reticulum ATP-dependent calcium pump activity. The increase was very rapid, being evident within 10 min of OTA administration and remained elevated for at least 6 hr thereafter. The increase in calcium pump activity was inconsistent with previous observations that OTA enhances lipid peroxidation (ethane exhalation) in vivo, a condition known to inhibit the calcium pump. However, no evidence of enhanced lipid peroxidation was observed in the renal cortex since levels of malondialdehyde and a variety of antioxidant enzymes including catalase, DT-diaphorase, superoxide dismutase, glutathione peroxidase, glutathione reductase and glutathione S-transferase were either unaltered or reduced. In in vitro studies, addition of OTA to cortex microsomes during calcium uptake inhibited the uptake process although the effect was reversible. Preincubation of microsomes with NADPH had a profound inhibitory effect on calcium uptake but inclusion of OTA was able to reverse the inhibition. Changes in the rates of microsomal calcium uptake correlated with changes in the steady-state levels of the phosphorylated Mg2+/Ca(2+)-ATPase intermediate, suggesting that in vivo/in vitro conditions were affecting the rate of enzyme phosphorylation.
...
PMID:Alterations in ATP-dependent calcium uptake by rat renal cortex microsomes following ochratoxin A administration in vivo or addition in vitro. 141 61

In order to identify comparative aspects of the interaction of calmodulin with its target proteins, proton magnetic-resonance studies of complex formation between calmodulin and defined segments of phospholamban and caldesmon have been undertaken. Residues 3-15 in the cytoplasmic region of phospholamban, an integral membrane protein of cardiac sarcoplasmic reticulum believed to regulate the calcium pumping ATPase, are shown to contribute to interaction with calmodulin. Using wheat germ calmodulin specifically modified with a spin-label to provide the spectral means for spatial localisation, these residues of phospholamban were correlated with binding in the vicinity of the probe attached to Cys-27 in the N-terminal domain of calmodulin. This interaction, relevant to the mechanism of calmodulin-dependent phosphorylation of phospholamban that relieves its inhibitory influence on the calcium pump, provides a useful model system for comparative study of the properties of calmodulin-binding domains. We contrast here a calmodulin-binding segment in the C-terminal region of caldesmon localised by 1H-NMR study of the interface(s) between the two proteins. These observations are discussed in the context of other calmodulin-binding sequences.
...
PMID:Interaction of calmodulin with phospholamban and caldesmon: comparative studies by 1H-NMR spectroscopy. 142 Mar 31

Magnesium-dependent ATPase (MgATPase) activity is associated with many E1-E2 or P-type transport ATPases including the sarcoplasmic reticulum (SR) calcium ATPase. The SR isolated from rat heart has a MgATPase activity which is 6-12 times faster than the MgATPase activity of the SR isolated from dog heart. To determine the origin of the high MgATPase activity of rat heart SR, we compared and contrasted cardiac SR isolated from both species. The preparations were similar in the following ways: (i) contamination by other organelles; (ii) the comigration of MgATPase activity with calcium-dependent ATPase (CaATPase) activity through a sucrose gradient; (iii) a similar ATPase activity sensitivity to pH and ATP concentration; (iv) the high and similar of sensitivity of ATPase activity to detergent; and (v) a similar protein profile. In both preparations, a single protein in the 105,000-Da region of polyacrylamide gels was phosphorylated by ATP, and the phosphorylated species was an acylphosphate formed in the presence and absence of calcium. Dimethyl sulfoxide, which slows acylphosphoenzyme breakdown, markedly inhibited both CaATPase and MgATPase activities of both preparations but not other enzyme activities. Importantly, the specific inhibitor of the SR calcium pump, thapsigargin, completely inhibited the CaATPase activity with an I50 of 6-7 nM; however, a higher concentration (I50 of 2 microM) was required to inhibit the MgATPase activity of the rat cardiac SR. These results provide evidence that the MgATPase activity of rat cardiac SR is part of the enzyme cycle of the calcium ATPase protein.
...
PMID:The MgATPase activity of rat cardiac sarcoplasmic reticulum is a function of the calcium ATPase protein. 144 68


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---