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

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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)

Cysteine residues of caldesmon were labeled with the fluorescent reagent N-(1-pyrenyl)maleimide. The number of sulfhydryl (SH) groups in caldesmon was around 3.5 on the basis of reactivity to 5,5'-dithiobis(2-nitrobenzoate); 80% of the SH groups were labeled with pyrene. The fluorescence spectrum from pyrene-caldesmon showed the presence of excited monomer and dimer (excimer). As the ionic strength increased, excimer fluorescence decreased, disappearing at salt concentrations higher than around 50 mM. The labeling of caldesmon with pyrene did not affect its ability to inhibit actin activation of heavy meromyosin Mg-ATPase and the release of this inhibition in the presence of Ca2+-calmodulin. Tropomyosin induced a change in the fluorescence spectrum of pyrene-caldesmon, indicating a conformational change associated with the interaction between caldesmon and tropomyosin. The affinity of caldesmon to tropomyosin was dependent on ionic strength. The binding constant was 5 x 10(6) M-1 in low salt, and the affinity was 20-fold less at ionic strengths close to physiological conditions. In the presence of actin, the affinity of caldesmon to tropomyosin was increased 5-fold. The addition of tropomyosin also changed the fluorescence spectrum of pyrene-caldesmon bound to actin filaments. The change in the conformation of tropomyosin, caused by the interaction between caldesmon and tropomyosin, was studied with pyrene-labeled tropomyosin. Fluorescence change was evident when unlabeled caldesmon was added to pyrene-tropomyosin bound to actin. These data suggest that the interaction between caldesmon and tropomyosin on the actin filament is associated with conformational changes on these thin filament associated proteins. These conformational changes may modulate the ability of thin filament to interact with myosin heads.
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PMID:Interaction between caldesmon and tropomyosin in the presence and absence of smooth muscle actin. 324 91

It is shown that cholesterol incorporation into the membranes of Zajdel hepatoma cells, lymphoblast leukemia cells L1210 and into those of ovary tumour causes an increase in the membrane phospholipid bilayer microviscosity measured by pyrene as fluorescent probe. The increase in the membrane lipid microviscosity resulted in a decrease in the activity of Na,K-ATPase and 5-nucleotidase of the tumour cells. After the injection of tumour cells with an increase of cholesterol/phospholipid ratio we observed an increase of the life-span of experimental animals as compared to the control groups.
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PMID:[Changes in the microviscosity of lipid bilayer membranes of various malignant cells and tumor transplantability]. 395 87

The fluorescence of pyrene-TM [rabbit skeletal tropomyosin (TM) labeled at Cys with N-(1-pyrenyl)maleimide] consists of monomer and excimer bands [Betcher-Lange, S., & Lehrer, S.S. (1978) J. Biol. Chem. 253, 3757-3760]; an increase in excimer fluorescence with temperature is due to a shift in equilibrium from a chain-closed state (N) to a chain-open state (X) associated with a helix pretransition [Graceffa, P., & Lehrer, S.S. (1980) J. Biol. Chem. 255, 11296-11300]. In this study, we show that the presence of appreciable excimer fluorescence at temperatures below the N----X pretransition (initial excimer) is due to perturbation of the TM chain-chain interaction by the pyrenes at Cys-190. Fluorescence and ATPase titrations indicated that the label caused a decrease in TM binding to F-actin primarily due to reduced end to end TM interactions on the actin filament. Under conditions where pyrene-TM was bound to F-actin, however, the excimer fluorescence did not increase with temperature, indicating that F-actin stabilizes tropomyosin by inhibiting the N----X transition. The binding of myosin subfragment 1 (S1) to pyrene-TM-F-actin at low ratios to actin caused time-dependent changes in fluorescence. After equilibrium was reached, the initial excimer fluorescence was markedly reduced and remained constant over the pretransition temperature range. Further stabilization of tropomyosin conformation on F-actin is therefore associated with S1 binding. Effects of the binding of S1 to the F-actin-tropomyosin thin filament on the state of tropomyosin were studied by monitoring the monomer fluorescence of pyrene-TM.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Fluorescence studies of the conformation of pyrene-labeled tropomyosin: effects of F-actin and myosin subfragment 1. 408 47

Treatment of adult female rats with a single dose of benzo[a]pyrene (BaP) fails to initiate preneoplastic enzyme-altered islands in their livers. Treatment with polychlorinated biphenyls (PCBs) at a dose which strongly induces aryl hydrocarbon(BaP)hydroxylase prior to BaP application and followed by promotion with PCBs causes the appearance of about 9 adenosine-5'-triphosphatase-deficient and 7 gamma-glutamyltranspeptidase-positive islands/cm2 after 12 weeks. PCB-pretreatment or promotion alone did not increase the BaP-dependent formation of islands above that of the PCB-treated controls (2-3 islands/cm2). The results suggest that upon alteration of its metabolism BaP causes the formation of preneoplastic lesions in the liver which become manifest by promotion.
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PMID:Benzo[a]pyrene initiates enzyme-altered islands in the liver of adult rats following single pretreatment and promotion with polychlorinated biphenyls. 613 22

Sarcoplasmic reticulum (SR) isolated from rabbit muscle was treated with N-ethyl-maleimide (NEM) to specifically inhibit the dephosphorylation step of the Ca2+,Mg2+-dependent ATPase reaction. However, when this membrane was solubilized with dodecyl octaethyleneglycol monoether (C12E8), rapid decomposition of the phosphoenzyme (EP) was observed both in the absence and presence of Mg2+. When the detergent was removed from the reaction mixture, the inhibition of EP decomposition by NEM was observed again. These results support our previous suggestion (1,2) that in the presence of high concentrations of C12E8, EP may be hydrolyzed to produce P1 in a manner different from the reaction in the native SR ATPase. Gel filtration of the solubilized ATPase was performed in the presence of low concentrations of C12E8 to elute ATPase aggregates of various sizes. Two distinct fractions were selected after column chromatography and their physical and kinetic properties were compared. The molecular weights of the ATPase proteins of these two fractions were determined to be about 150 and 360K daltons with Stokes radii of about 5.5 and 8.0 nm, respectively. The Stokes radii agreed with the values obtained from polarization decay measurement data of N-1-pyrene maleimide (N-1-P)-labeled ATPase aggregates separated on the same column. The rate of EP decomposition was determined for the two column fractions described above. After the addition of EDTA the EP decomposition rate of the smaller-sized ATPase was much higher than the EP decomposition rate of the larger-sized ATPase.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparative study of the kinetic and structural properties of monomeric and oligomeric forms of sarcoplasmic reticulum ATPase. 614 42

Sarcoplasmic reticulum ATPase from fast skeletal muscle was labeled in native vesicles with N-(3-pyrene)maleinimide. At labeling ratios larger than 1 mol pyrenemaleinimide/2.5 mol ATPase significant amounts of excimers are detected. Excimer concentration decreases at low, non-solubilizing amounts of detergents (0.2 mg X mg protein-1) and completely disappears after solubilization of the membranes. These results exclude that excimers are formed due to 'double-labeling' of one ATPase molecule. It is concluded that the ATPase exists as an oligomer within the membrane of native vesicles.
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PMID:Excimer formation of ATPase from sarcoplasmic reticulum labeled with N-(3-pyrene)maleinimide. 621 89

Studies were carried out of temperature relationship of dansylchloride, N-3-pyrenylmaleinimide fluorescence, SR membranes, self-luminescence caused by Ca-ATPase tryptophane - provided fluorescence and of pyrene excimerization in membrane preparations of sarcoplasmic reticulum (SR) of rabbit skeletal muscles. Temperature relationship of fluorescence intensity of dansylchloride and N-3-pyrenylmaleimide in Arrhenius coordinates has bends at 15 and 35 degrees. Selffluorescence of protein samples linearly depends on temperature. Temperature relationship of the ratio between the intensities of exsimeric and monomeric forms of pyrene Fa/Fm in Arrhenius coordinates has the bend at 20-22 degrees. Hence only the latter relationship coincides with the shape of Arrhenius graph for enzymatic activity of SR Ca-ATPase.
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PMID:[Effect of temperature on fluorescence of labels and probes of various localizations incorporated into sarcoplasmic reticulum samples]. 621 13

Fluorescence polarization and formation of excimers were studied in N-(3-pyrene)maleinimide-labeled sarcoplasmic reticulum vesicles. 1. The polarization of pyrenemaleinimide labeled vesicles does not change with temperature and shows a pronounced decrease at labeling concentrations larger than 1 mol pyrenemaleinimide per 10 mol ATPase. 2. Solubilization of the membrane with myristoylglycerophosphocholine renders the polarization temperature dependent, but does not affect the concentration dependent depolarization observed in native vesicles. 3. The polarization of labeled vesicles is much smaller than to be expected from the temperature independent polarization indicating that the pyrenemaleinimide polarization did not monitor the rotation of the entire ATPase. Thus segmental motion occurs. 4. Pyrene excimers are observed at label concentrations larger than 1 mol label per 2.5 mol ATPase. 5. The amount of excimers was critically dependent on added detergents. From the fact that non-solubilizing amounts of myristoylglycerophosphocholine strongly reduced the amount of pyrene excimers it is concluded that in the native sarcoplasmic reticulum vesicles at least two ATPase molecules must be in close contact.
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PMID:Fluorescence studies on N-(3-pyrene)maleinimide-labeled sarcoplasmic reticulum ATPase in native and solubilized membranes. 622 51

The quenching of the intrinsic protein fluorescence of sarcoplasmic reticulum Ca-ATPase from the rabbit skeletal muscles by hydrophylic (NaI, CsCl) or hydrophobic (pyrene, fluorescamine) substances has been studied. CsCl (up to 1 M) has been shown not to affect the intrinsic protein fluorescence while NaI (250 mM) quenches it at 15%, pyrene (8 mkM) decreases the intrinsic fluorescence of Ca-ATPase at 35% and fluorescamine (up to 40 mkM)--at 80%. Possible mechanisms of the interaction of the quenchers with the intrinsic fluorescence of sarcoplasmic reticulum Ca-ATPase are being discussed.
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PMID:[Ca-ATPase self-fluorescence in the sarcoplasmic reticulum of the rabbit skeletal muscle]. 623 30

The time-course of ATP hydrolysis by Ca-ATPase of purified sarcoplasmic reticulum is biphasic with an initial rate over 1 to 2 min exceeding the subsequent rate. Hydrolysis of GTP and p-nitrophenylphosphate (pNPP) occurs at a slower but constant rate. Arrhenius plots of GTP, p-nitrophenylphosphate and initial rates of ATP hydrolysis all exhibit a discontinuity at about 20-24 degrees C; no breaks are observed in plots of the slower phase of ATP hydrolysis. The effect of substrate hydrolysis on the disposition of the enzyme in the membrane was examined by monitoring the quenching of tryptophan fluorescence by pyrene present in the hydrophobic domain of the membrane. The presence of ATP, but not GTP, prevents a temperature-dependent decrease in fluorescence quenching suggesting that ATP binding causes a change in the protein domain in contact with the membrane lipids.
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PMID:The modulation of Ca-ATPase activity and protein-lipid interactions in the sarcoplasmic reticulum by ATP. 623 16


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