Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The maintenance of intracellular Ca2+ homeostasis is critical to many cellular functions that rely on the calcium ion as a messenger. While attempting to characterize the effects of lead on intracellular calcium levels ([Ca2+]i) in LLC-MK2 Rhesus Monkey kidney cells, we observed that treatment with the metal chelating drug, meso-2,3-dimer-captosuccinic acid (DMSA) evoked transient increases in [Ca2+]i. Changes in [Ca2+]i were monitored using the Ca2+ indicator dye Fura-2 and a dual wavelength fluorescence imaging system. In the presence of 2 mM extracellular Ca2+, DMSA treatment caused a concentration-dependent (15-500 microM) transient increase in [Ca2+]i returning to baseline levels within 30-60 s. Pharmacologic concentrations of DMSA (30 microM) stimulated a three-fold increase in [Ca2+]i, which was spatiotemporally comparable to Ca2+ transients induced by other calcium agonists. Depletion of inositol trisphosphate (IP3)-sensitive [Ca2+]i stores with the smooth endoplasmic reticulum calcium-ATPase (SERCA) inhibitor thapsigargin did not prevent DMSA-elicited increases in [Ca2+]i, suggesting that Ca2+ mobilized by DMSA was either extracellular or from an non-IP3 releasable Ca2+ pool. Treatment with glutathione, cysteine, or 2-mercaptoethanol caused similar but not identical calcium transients. Adenosine-5'-trisphosphate (ATP) also elicited transient increases in [Ca2+]i similar to those of DMSA. No transient increases in [Ca2+]i were elicited by DMSA or ATP in the absence of extracellular calcium. These data indicate that DMSA and other sulfhydryl compounds trigger an influx of extracellular calcium, suggesting a previously unobserved and unanticipated interaction between DMSA and the Ca2+ messenger system.
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PMID:Meso-2,3-dimercaptosuccinic acid induces calcium transients in cultured rhesus monkey kidney cells. 1057 85

We have synthesized the luminescent and fluorescent lanthanide chelate S-(2-nitro-5-thiobenzoic acid)cysteaminyldiethylenetriaminepentaacetate-5-[(2-aminoethyl)am ino ]naphthalene-1-sulfonic acid as well as the fluorescent analogue S-(2-nitro-5-thiobenzoic acid)cysteaminyl-5-carboxyfluorescein using the procedure we recently described [Bertrand, R., Capony, J.-P., Derancourt, J., and Kassab, R. (1999) Biochemistry 38, 11914-11925]. Both mixed disulfides react with the skeletal myosin motor domain (S-1) as actin site-directed agents and label exclusively and stoichiometrically Cys 540 in the hydrophobic strong actin binding helix-loop-helix motif, causing only a 1.9-2.4-fold decrease in the V(max) for acto-S-1 ATPase. The covalently attached cysteaminyl probe side chain spans maximally 17 and 8 A, respectively, and the fluorophores have different polarity, volume, and flexibility. Thus, they may provide complementary spectroscopic information on the environmental properties of this critical actin binding region. Here, we have analyzed by extrinsic fluorescence spectroscopy S-1 derivatized with the fluorescein label or with the Tb(3+) or Eu(3+) chelate of the other label to assess the conformational transitions precisely occurring at this site upon interaction with F-actin, nucleotides, or phosphate analogues. For either label, specific spectral changes of significant amplitude were obtained, identifying at least two major structural states. One was mediated by rigor binding of F-actin in the absence or presence of MgADP. It was abolished by MgATP, and it was not produced by the binding of nonpolymerizable G-actin. A modeling of the corresponding changes in the intensity and lambda(max) of the fluorescence emission spectra, achieved using the fluorescent adducts of 2-mercaptoethanol in varying concentrations of dimethylformamide, illustrates the predicted apolar nature of the strong acto-S-1 interface. A second state was promoted by the binding of ATP, AMP-PNP, ADP.AlF4, ADP. BeFx, or PP(i). It should be prevalent in the weak acto-S-1 binding complexes. The accompanying fluorescence intensity reduction, observed with each label, in both the absence and presence of F-actin, would result from a specific modification by these ligands of the probe orientation and/or solvent accessibility as suggested by acrylamide quenching experiments. It could represent the spectral manifestation of the predicted allosteric linkage from the ATPase site to the strong actin binding site of S-1 that modulates the acto-S-1 affinity. Our study offers the basis necessary for further detailed spectroscopic investigations on the conformational dynamics in solution of the stereospecific and hydrophobic actin binding motif during the skeletal cross-bridge cycle.
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PMID:Fluorescence characterization of structural transitions at the strong actin binding motif in skeletal myosin affinity labeled at cysteine 540 with novel spectroscopic cysteaminyl mixed disulfides. 1108 19

The thermal unfolding and domain structure of Na+/K+-ATPase from pig kidney were studied by high-sensitivity differential scanning calorimetry (HS-DSC). The excess heat capacity function of Na+/K+-ATPase displays the unfolding of three cooperative domains with midpoint transition temperatures (Td) of 320.6, 327.5, 331.5 K, respectively. The domain with Td = 327.5 K was identified as corresponding to the beta subunit, while two other domains belong to the alpha subunit. The thermal unfolding of the low-temperature domain leads to large changes in the amplitude of the short-circuit current, but has no effect on the ATP hydrolysing activity. Furthermore, dithiothreitol or 2-mercaptoethanol treatment causes destruction of this domain, accompanied by significant disruption of the ion transporting function and a 25% loss of ATPase activity. The observed total unfolding enthalpy of the protein is rather low (approximately 12 J.g-1), suggesting that thermal denaturation of Na+/K+-ATPase does not lead to complete unfolding of the entire molecule. Presumably, transmembrane segments retain most of their secondary structure upon thermal denaturation. The binding of physiological ligands results in a pronounced increase in the conformational stability of both enzyme subunits.
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PMID:The thermal unfolding and domain structure of Na+/K+-exchanging ATPase. A scanning calorimetry study. 1158 93

The reactions of omeprazole, a potent proton pump inhibitor (PPI) were investigated in the presence of 2-mercapotoethanol. Reactions were monitored in solutions buffered to pH values ranging 2.0-8.0 using differential pulse polarography (DPP) at the static mercury drop electrode (SMDE). The fast, sensitive and selective electrochemical technique facilitated successive recordings of voltammograms (peak current (nA) vs. peak potential (volts vs. Ag/AgCl)) for all analytes in situe, including the 2-mercaptoethanol. In acidic solutions and in the presence of 2-mercaptoethanol, omeprazole undergoes degradation into three compounds, the first is a cyclic sulfenamide (D+), previously believed to be the active inhibitor of the H+, K+-ATPase, the second is the omeprazole dimer, and the third is the disulfide believed to be the product of reaction between 2-mercaptoethanol and D+. The cyclic sulfenamide (D+) solution was found to be stable in solutions containing 2-mercaptoethanol having pH values: 2.0, 4.0, and 6.0. This finding proved conclusively that the cyclic sulfenamide is not reactive toward the 2-mercaptoethanol. In contrast to previous reports, the conversion of the sulfenic acid intermediate into D+ was found to be irreversible. Due to this irreversibility, D+ and sulfenic acid were not rapidly interconvertable. The present work suggests that the active inhibitor is the sulfenic acid.
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PMID:Reactions of sulfenic acid with 2-mercaptoethanol: a mechanism for the inhibition of gastric (H+-K+)-adenosine triphosphate by omeprazole. 1699 72

A four- to seven-fold enhancement of leaf hydraulic conductance by light has been reported in three temperate tree species. The enhancement occurs in the liquid-flow pathway between the petiole and the site of water evaporation. The enhancement occurs within 1 h, and dissipates in darkness over a period of 1 to 10 h depending on species. Here we report light-induced enhancement of leaf hydraulic conductance in a fourth species, bur oak (Quercus macrocarpa Michx.), the dependence of the effect on light flux and color, its absence in leaves of seedlings, and the impact on the response of leaf vein severance and several metabolic inhibitors. The light response of leaf hydraulic conductance approached saturation at a photosynthetic photon flux of 150 mumol m(-2) s(-1). Hydraulic enhancement was greater in response to blue and green light than to visible radiation of longer wavelengths, although at the same irradiance, the response to white light was greater than to light of any single color. Atrazine (a photosystem II inhibitor), fusicoccin (which stimulates plasma membrane-bound H(+)-ATPase) and HgCl(2) (an aquaporin blocker) reduced the light response of leaf lamina hydraulic conductance. When 2-mercaptoethanol was added following mercury treatment, the light response was totally suppressed. Our results are consistent with the notion that the effect of light on leaf lamina hydraulic conductance is controlled by factors acting outside the leaf veins, possibly through light-induced changes in membrane permeability of either mesophyll or bundle sheath cells, or both.
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PMID:Light response of hydraulic conductance in bur oak (Quercus macrocarpa) leaves. 1845 May 65


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