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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Incubation of the Ca2+,Mg2+-activated adenosine triphosphatase of Escherichia coli with phospholipid vesicles resulted in binding of the enzyme to the lipid. Binding was observed with vesicles of soybean phospholipid (asolectin), phosphatidyglycerol, phosphatidylserine, phosphatidylcholine, and cardiolpin. Binding was not affected by alterations in pH in the range of pH 6.5 to 8.5, by ionic strength, or by the presence of Mg2+. Loss of the delta subunit from the enzyme had no effect on binding. However, removal of the delta and epsilon subunits by treatment of the enzyme with trypsin prevented binding to phospholipid. This treatment also removed a small portion (less than 2000 daltons) of the alpha subunit. It is concluded that the ATPase of E. coli binds to phospholipid vesicles mainly by nonpolar interactions through the alpha and (or) epilson subunits of the enzyme.
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PMID:Binding of the Ca2+,Mg2+-activated adenosine triphosphatase of Escherichia coli to phospholipid vesicles. 14 87

The subcellular distribution of calcium-stimulated adenosine triphosphatase in the albino rabbit dental pulp was studied. The purity of the microsomal fraction was examined by measuring the marker enzymes and by electron microscopic observation. Some properties of calcium-stimulated adenosine triphosphatase were investigated.
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PMID:Studies on calcium-stimulated adenosine triphosphatase in the albino rabbit dental pulp. Its subcellular distribution and properties. 15 Apr 33

The effect of lipid peroxidation on the Ca2+-accumulating and Ca2+-retaining abilities of the microsomal fraction from chicken breast muscle was investigated. At 25 degrees C, enzymic lipid peroxidation did not seriously affect either of these abilities unless ascorbic acid was present, when both were diminished. At 37 degrees C, Ca2+-concentrating ability was decreased further by the effects of heat damage to the membrane. Membrane lipid peroxidation did not affect microsomal adenosine triphosphatase activity unless the microsomal fraction was subsequently washed with albumin. This effect of albumin is possibly due to removal of lipid-breakdown products. Addition of soya-bean phospholipids to the peroxidized vesicles washed with albumin restored adenosine triphosphatase activity, demonstrating a non-specific phospholipid requirement.
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PMID:The effect of lipid peroxidation on the calcium-accumulating ability of the microsomal fraction isolated from chicken breast muscle. 15 35

Primary and secondary fragments of the Ca2+-adenosine triphosphatase from sarcoplasmic reticulum are resistant to complete denaturation by guanidinium hydrochloride, a property characteristic of many intrinsic membrane proteins. None of the fragments display a single cooperative transition from ordered structure to random coil suggesting each fragment contains several domains of differing resistance to guanidinium hydrochloride denaturation. The data suggest that the native enzyme has at least three membrane-embedded domains, with an externally accessible link between each.
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PMID:Denaturation of the tryptic fragments of the calcium (II) adenosine triphosphatase from sarcoplasmic reticulum by guanidinium hydrochloride. 15 19

The effect of several tetracycline antibiotics of human erythrocytes was examined because of previous findings that these drugs bind to erythrocyte membranes. Minocycline and cetocycline, two highly lipid-soluble analogues, but not tetracycline, induced loss of K+ from red blood cells. Loss of K+ increased linearly with time of incubation, concentration of minocycline, and temperature. The effect of minocycline was inhibited by plasma and calcium. The cells from one volunteer consistently showed an augmented response to minocycline; similar findings for family members of the volunteer suggested a dominant autosomal mode of inheritance. The only abnormality noted in the subject was mild reticulocytosis and a slightly reduced K+ content in his red blood cells. Preliminary studies did not demonstrate alterations in protein composition of his red blood cell membranes, enhanced osmotic fragility, or defects in Ca++-dependent or ouabain-sensitive (Na+-K+)-dependent adenosine triphosphatase activity. The exact site of the minocycline effect remains to be determined.
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PMID:Minocycline-induced loss of potassium from erythrocytes: identification of a family with an augmented response. 15 37

A pure, enzymatically active Ca2+-dependent adenosine triphosphatase (Ca2+-ATPase) has been isolated from canine ventricular sarcoplasmic reticulum. In contrast to that derived from skeletal muscle, the Ca2+-ATPase from cardiac sarcoplasmic reticulum was more active when solubilization and subsequent purification took place in the presence of its substrates, Ca2+ and ATP. Cholate- or deoxycholate-solubilized Ca2+-ATPase is recovered following rapid glycerol dilution and centrifugation. The Ca2+-ATPase is stable and possesses hydrolytic capacities up to 4 mumol/mg/min. Sodium dodecyl sulfate-polyacrylamide gels reveal the presence of one protein in the range of 95,000 to 100,000 daltons. This method also yields purified Ca2+-ATPase from fast skeletal muscle of similar activities to those reported by other laboratories.
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PMID:Rapid purification of canine cardiac sarcoplasmic reticulum Ca2+-ATPase. 15 59

The pattern of response of the intestinal enzymes Ca2+-activated adenosine triphosphatase and alkaline phosphatase in the chick to 1,25-dihydroxycholecalciferol is consistent with a role for the former but not the latter enzyme in the vitamin D-dependent absorption of calcium.
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PMID:Differentiation of the changes in alkaline phosphatase from calcium ion-activated adenosine triphosphatase activities associated with increased calcium absorption in chick intestine. 15 34

1. The steady-state kinetic behaviour of the ATPase (adenosine triphosphatase) of intact myofibrils was studied in the presence of both high and low concentrations of Ca2+ (0.25 mM and less than 10 nM respectively). 2. Kinetic data were collected over the initial linear phase of the assay, which lasts for 20--60s. To obtain consistent data we found it necessary to use either fresh myofibril preparations or preparations that had been stored in the presence of thiol compounds. 3. When assayed in the presence of 0.25 mM-Ca2+, the myofibrillar ATPase obeyed Michaelis-Menten kinetics over the range 0.03--5.0 mM-MgATP (Km 16 +/- 6 micrometer, V 0.4 +/- 0.1 mumol/min per mg). 4. At low Ca2+ concentrations (less than 10 nM) the myofibrillar ATPase displayed pronounced substrate inhibition, which was not observed at high Ca2+ concentrations. Thus increasing the MgATP concentration had the net effect of decreasing the ATPase activity at low Ca2+ relative to that at high Ca2+. This preferential effect of MgATP on the low-Ca2+ ATPase may be important in Ca2+ control. 5. The substrate inhibition that was observed at low Ca2+ was lost on storage or thiol modification of the myofibrils. 6. Under physiological conditions (2 mM-MgATP, I 0.15, pH 7.0), the ATPase of fresh and thiol-protected myofibrils displayed approx. 100-fold activation by Ca2+.
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PMID:Kinetics and regulation of the myofibrillar adenosine triphosphatase. 15 23

The effect of indomethacin, which is a nonsteroidal anti-inflammatory drug, on Ca2+-stimulated adenosine triphosphatase (Ca2+-ATPase) activity in the microsomes of rat submandibular gland was investigated. The effect of aspirin on Ca2+-ATPase activity was also studied.
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PMID:Effect of indomethacin on Ca2+-stimulated adenosine triphosphatase in the microsomes of rat submandibular gland. 15 2

Human erythrocyte and bovine brain calmodulins were indistinguishable by tryptic peptide mapping, indicating that the primary sequence of the two proteins is either very similar or identical. Calcium binding determinations of human erythrocyte calmodulin, by equilibrium dialysis and fluorescence titration, were in close agreement with previous studies on other calmodulins. The calcium-activated adenosine triphosphatase which is stimulated by calmodulin was shown to be firmly associated with smooth erythrocyte plasma membranes devoid of spectrin and actin. Kinetic titration demonstrated that there are 4500 calmodulin binding sites per erythrocyte and that the turnover number of this calcium-activated adenosine triphosphatase is 3000 mumol of Pi . (mumol of site)-1 . min-1 which is similar to the turnover numbers of other transport adenosine triphosphatases. Furthermore, calmodulin stimulates calcium-activated adenosine triphosphatase by a simple enzyme-ligand association.
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PMID:Human erythrocyte calmodulin. Further chemical characterization and the site of its interaction with the membrane. 15 56


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