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:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mg2+-dependent Ca2+-activated ATPase of microsoma fraction from the grey matter of cerebral great hemispheres determined after the preliminary treatment of the preparation with 0.1% digitonin, while preserved in the medium with 10 mM mercaptoethanol for seven days at a temperature of 4-6 degrees C is inactivated by 10-15% and approximately by 50% while preserved without mercaptoethanol. Mercaptoethanol does not make reactivating effect. SH-reagents at definite concentrations completely inhibit the activity of Mg2+, Ca2+-ATPase. Half-maximum inhibition of the enzyme is reached with the salirgan, p-CMB and NEM concentrations of 5-10(-6) M, 5-10(-6) M and 5-10(-3) M, respectively. Mg2+-ATPase is not suppressed completely, and at high concentrations of SH-reagents the residual activity is 1.3 muM of Pi per 1 mg of protein in 1 hr. ATP in the concentrations optimal for manifestation of Mg2+, Ca2+-ATPase (3 mM) efficiently protects the enzyme from the inactivating effect of NEM. This gives reasons to suppose that the active centre of Mg2+, Ca2+-ATPase contains an SH-group. The quantity of SH-groups readily accessible of the Ellman reactive in the initial preparation of the brain microsomes is 45 + 2.0 nM per 1 mg of protein and in the preparation dissolved in 2.5% sodium dodecyl sulphate, 110 + 7.8 nmM per 1 mg of protein. In the presence of 0.1% digitonin the quantity of SH-groups of the preparation is 55 + 3.5 nM per 1 mg of protein, simultaneously such treatment of detergent results in manifestation of Mg2+, Ca2+-ATPase activity. An inactivating effect of SH-reagents and the protective effect of ATP indicate similarity of the enzyme under study to Mg2+, Ca2+-ATPase of sarcoplasmatic reticulum.
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PMID:[SH-group and Mg2+-dependent Ca2+-activated ATPase activity of the microsome fraction of the brain]. 12 70

A comparison is made between dynein [flagellar ATPase; EC 3.6.1.3], purified from sea urchin sperm flagella, and muscle myosin. The amino acid composition of dynein was found to be statistically different from that of myosin. The same was true of their tryptic fragments retaining ATPase activity, i.e., Fragment A of dynein and heavy meromyosin. At low ionic strength, no superprecipitation took place when ATP was added to a mixture of dynein and actin, and stimulation of the Mg2+-ATPase activity of dynein remained below 50% even when a one-hundred-fold excess of actin was present. No viscosity drop was caused by adding ATP to a solution containing dynein and actin. Anti-myosin antiserum did not react with dynein, while anti-Fragment A antiserum formed no precipit-n line against myosin. Furthermore, the amount of dynein that combined with F-actin was less than one-fifth of the amount of dynein that fully combined with microtubules. These results are consistent with the dissimilarity in enzymatic and other physiocochemical properties of these two proteins.
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PMID:Amino acid composition of dynein and comparison with myosin. 12 68

A contractile protein closely resembling natural actomyosin (myosin B) of rabbit skeletal muscle was extracted from plasmodia of the slime mold, Physarum polycephalum, by protecting the SH-groups with beta-mercaptoethanol or dithiothreitol. Superprecipitation of the protein induced by Mg2+-ATP at low ionic strength was observed only in the presence of very low concentrations of free Ca2+ ions, and the Mg2+-ATPase [EC 3.6.1.3] reaction was activated 2- to 6-fold by 1 muM of free Ca2+ ions. Crude myosin and actin fractions were separated by centrifuging plasmodium myosin B in the presence of Mg2+-PPi at high ionic strength. The crude myosin showed both EDTA- and Ca2+-activated ATPase activities. The Mg2+-ATPase activity of crude myosin from plasmodia was markedly activated by the addition of pure F-actin from rabbit skeletal muscle. Addition of the F-action-regulatory protein complex prepared from rabbit skeletal muscle as well as the actin fraction of plasmodium caused the same degree of activation as the addition of pure F-actin only in the presence of very low concentrations of Ca2+ ion
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PMID:Ca2+-sensitivity of actomyosin ATPase purified from Physarum polycephalum. 13 90

H-Meromyosin (HMM) was digested with insoluble papain [EC 3.4.22.2]. Neither the size of the initial burst of Pi liberation (0.5 mole/mole of myosin head) nor the Mg2+-ATPase [EC 3.6.1.3] activity of HMM in the steady state was affected by this treatment. Acto-S-1 was obtained by mixing F-actin with HMM digested with insoluble papain (HMM-S-1). The size of the initial burst of Pi liberation of acto-S-1 was 0.35 mole/mole of S-l at an ATP concentration of 0.5 mole/mole of S-1, and 0.5 mole/moleof S-1 at ATP concentrations above 1 mole/mole of S-1...
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PMID:Separation of subfragment-1 of H-meromyosin into two equimolar fractions with and without formation of the reactive enzyme-phosphate-ADP complex. 13 97

Lipophilic metal chelators inhibit various energy-transducing functions of chloroplasts. The following observations were made 1. Photophosphorylation coupled to any known mode of electron transfer, i.e. whole-chain noncyclic, the partial noncyclic Photosystem I or Photosystem II reactions, or cyclic, is inhibited by several lipophilic chelators, but not by hydrophilic chelators. 2. The light- and dithioerythritol-dependent Mg2+-ATPase was also inhibited by the lipophilic chelators. 3. Electron transport through either partial reaction. Photosystem I or Photosystem II was not inhibited by lipophilic chelators. Whole-chain coupled electron transport was inhibited by bathophenanthroline, and the inhibition was not reversed by uncouplers. The diketone chelators diphenyl propanedione and nonanedione inhibited the coupled, whole-chain electron transport and the inhibition was reversed by uncouplers, a pattern typical of energy transfer inhibitors. The electron transport inhibition site is localized in the region of platoquinone leads to cytochrome f. This inhibition site is consistent with other recent work (Prince et al. (1975) FEBS Lett. 51, 108 and Malkin and Aparicio (1975) Biochem. Biophys. Res. Commun. 63, 1157) showing that a non-heme iron protein is present in chloroplasts having a redox potential near + 290 mV. A likely position for such a component to function in electron transport would be between plastoquinone and cytochrome f. just where our data suggests there to be a functional metalloprotein. 4. Some of the lipophilic chelators induce H+ leakiness in the chloroplast membrane, making interpretation of their phosphorylation inhibition difficult. However, 1-3 mM nonanedione does not induce significant H+ leakiness, while inhibiting ATP formation and the Mg2+-ATPase. Nonanedione, at those concentrations, causes a two- to four-fold increase in the extent of H+ uptake. 5. These results are consistent with, but do not prove, the involvement of a non-heme iron or a metalloprotein in chloroplast energy transduction.
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PMID:Inhibition of energy-transducing functions of chloroplast membranes by lipophilic iron chelators. 13 88

Actin, myosin, and a high molecular weight actin-binding protein were purified from chronic myelogenous leukemia (CML) leukocytes. CML leukocyte actin resembled skeletal muscle and other cytoplasmic actins by its subunit molecular weight, by its ability to polymerize in the presence of salts, and to activate the Mg2+-ATPase activity of rabbit skeletal muscle myosin. CML leukocyte myosin was similar to other vertebrate cytoplasmic myosins in having heavy chains and two light subunits. However, its apparent heavy-chain molecular weight and Stokes radius suggested that it was variably degraded during purification. Purified CML leukocyte myosin had average specific EDTA- AND Ca2+-activated ATPase activities of 125 and 151 nmol Pi released/mg protein per min, respectively and low specific Mg2+-ATPase activity. The Mg2+-ATPase activity of CML myosin was increased 200-fold by rabbit skeletal muscle F-actin, but the specific activity relative to that of actin-activated rabbit skeletal muscle myosin was low. CML leukocyte myosin, like other vertebrate cytoplasmic myosins, formed filaments in 0.1 M KCl solutions. Reduced and denatured CML leukocyte-actin-binding protein had a single high molecular weight subunit like a recently described actin-binding protein of rabbit pulmonary macrophages which promotes the polymerization and gelation of actin. Cytoplasmic extracts of CML leukocytes prepared with ice-cold 0.34-M sucrose solutions containing Mg2+-ATP, dithiothreitol, and EDTA at pH 7.0 underwent rapid gelation when warmed to 25 degrees C. Initially, the gel could be liquified by cooling to ice-bath temperature. With time, warmed cytoplasmic extract gels shrunk ("contracted") into aggregates. The following findings indicated that CML leukocyte actin-binding protein promoted the temperature-dependent gelation of actin in the cytoplasmic extracts and that CML leukocyte myosin was involved in the contraction of the actin gels: (a) Cytoplasmic extract gels initially contained actin as their major polypeptide component and consistent of tangled thin filaments; (b) Contracted aggregates of cytoplasmic extract gels contained by large quantities of myosin as well as actin; (c) Purified actin-binding protein underwent a temperature-dependent, reversible aggregation and caused low concentrations of purified muscle or CML leukocyte actins to gel in sucrose solutions; (d) The gels formed from purified actin plus purified actin-binding protein slowly contracted in the presence but not in the absence of purified CML leukocyte myosin; (e) Rabbit antiserum against purified CML leukocyte actin-binding protein but not against purified CML leukocyte myosin inhibited the gelation of warmed CML leukocyte extracts. Antiserum against CML leukocyte myosin had no effect on the gelation of CML leukocyte extracts but partially curtailed the contraction of the CML leukocyte extract gels and of gels formed from purified CML leukocyte actin-binding protein plus rabbit skeletal muscle actin.
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PMID:Interactions of actin, myosin, and an actin-binding protein of chronic myelogenous leukemia leukocytes. 13 21

A highly purified preparation of myosin from Physarum polycephalum has been shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis to contain heavy chains and only one molecular weight class of light chains, of approx. 15 000 daltons. Kinetic investigations of the Ca2+-ATPase and Mg2+-ATPase (ATP phosphohydrolases, EC 3.6.1.3) at pH 8.0 gave Km and V values of 17.3 muM and 1.25 mumol Pi/min per mg, and 2.4 muM and 0.12 mumol Pi/min per mg, respectively. Adenylyl imidodiphosphate, a beta-gamma-imido ATP analog, inhibited the ATPase activity of Physarum myosin competitively with Ki values equal to 350 and 12 muM in the presence of Ca2+ and Mg2+, respectively. The ATPase activity of Physarum myosin was inhibited at a very low rate (t1/2 = 24 h) by the ATP analog, 6,6'-dithiobis(inosinyl imidodiphosphate), with concentrations of inhibitor previously shown to inactivate (t1/2 approximately 10 min) skeletal and cardiac myosins rapidly by reacting with key cysteines.
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PMID:Observations on the kinetics, subunit composition, and sulfhydryl reactivity of myosin from Physarum polycephalum. 13 51

1. The transduction of energy from the oxidation of substrates by the electron transport chain or from the hydrolysis of ATP by the Mg2+-ATPase was measured in everted membrane vesicles of Escherichia coli using the energy-dependent quenching of quinacrine fluorescence and the active transport of calcium. 2. Treatment of everted membranes derived from a wild-type strain with the chaotropic agents guanidine-HC1 and urea caused a loss of energy-linked functions and an increase in the permeability of the membrane to protons, as measured by the loss of respiratory-linked proton uptake. 3. The coupling of energy to the quenching of quinacrine fluorescence and calcium transport could be restored by treatment of the membranes with N,N'-dicyclohyexylcarbodiimide. 4. Chaotrope-treated membranes were found to lack Mg2+-ATPase activity. Binding of crude soluble Mg2+-ATPase to treated membranes restored energy-linked functions. 5. Membranes prepared from a wild-type strain grown under anaerobic conditions in the presence of nitrate retained respiration-linked quenching of quinacrine fluorescence and active transport of calcium after treatment with chaotropic agents. 6. Everted membrane vesicles prepared from an Mg2+-ATPase deficient strain lacked respiratory-driven functions when the cells were grown aerobically but were not distinguishable from membranes of the wild-type when both were grown under anaerobic conditions in the presence of nitrate. 7. It is concluded (a) that chaotropic agents solubilize a portion of the Mg2+-ATPase, causing an increase in the permeability of the membrane to protons and (b) that growth under anaerobic conditions in the presence of nitrate prevents the increase in proton permeability caused by genetic or chemical removal of the catalytic portion of the Mg2+-ATPase.
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PMID:Energy transduction in Escherichia coli. The effect of chaotropic agents on energy coupling in everted membrane vesicles from aerobic and anaerobic cultures. 13 39

Spontaneously hypertensive rats (SHR) and two strains of normotensive rats were compared with respect to enzymatic activities and calcium accumulation of plasma membrane and endoplasmic reticulum enriched fractions from their mesenteric arteries. Increased specific activities of alkaline phosphatase, 5'-nucleotidase and Mg2+-ATPase, and increased ATP-dependent calcium accumulation were found in 5- to 6-month-old SHR as compared to both strains fo age-matched normotensive rats. Alkaline phosphatase was increased in 33-day-old "early hypertensive" and 3- to 4-month-old SHR, but 5'-nucleotidase, Mg2+-ATPase, and calcium accumulation were not. Hydralazine treatment of young SHR partially prevented the increase of both alkaline phosphatase activity and blood pressure that develops with age. The relationship between alkaline phosphatase activity and the alterations in vascular reactivity associated with hypertension remains to be determined.
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PMID:Relationship between blood pressure of spontaneously hypertensive rats and alterations in membrane properties of mesenteric arteries. 13 88

Kinetic measurement of the reaction of dynein ATPase (ATP phosphohydrolase, EC 3.6.1.3) extracted from the gills of Mytilus edulis shows that in the presence of Mg2+ there is a very rapid initial liberation of Pi from the dynein-ATP system, followed by a slower liberation in the steady state. In view of following results, we have confirmed that this phenomenon is not due to the accumulation of end products, a fall in substrate concentration, nor to the presence of labile impurities in ATP but is due to the catalytic activity of dynein ATPase. 1. The replacement of native dynein by heat denatured dynein or other kinds of Mg2+-ATPase could not produce such a burst phenomenon under the same condition. 2. Both the rate of initial burst and that of steady state were proportional to enzyme content over a wide range under our standard condition. 3. Initial burst was also observed under the constant ATP level by using a ATP generate system. 4. Preincubation of dynein with Pi prior to initiation of the reaction did not eliminate the initial burst. Some properties of the initial rapid liberation of dynein ATPase were also examined. These are shown below. 5. The free ADP liberation did not show any initial burst though the Pi liberation did in the initial phase and the rate of free ADP liberation was almost equal to that of Pi liberation of the steady state. 6. Mg2+ was more effective than Ca2+ for the appearance of the initial burst while the liberation of Pi in the steady state was activated more by Ca2+ than by Mg2+. The addition of K+ in the presence of Mg2+ resulted in a marked increase of Pi liberation in the steady state but not in the initial state. 7. The activation energy of the initial burst was 9.7 kcal, which is slightly smaller than that of myosin ATPase.
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PMID:Studies on the initial phase of dynein ATPase activity. 13 33


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