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)

Purified goblet cell apical membranes from Manduca sexta larval midgut exhibit a specific ATPase activity approx. 20-fold higher than that in the 100 000 X g pellet of a midgut homogenate. The already substantial ATPase activity in this plasma membrane segment is doubled in the presence of 20-50 mM KCl. At ATP concentrations ranging from 0.1 to 3.0 mM, the presence of 20 mM KCl leads to a 10-fold increase in the enzyme's affinity for ATP. ATPase activity is greatest at a pH of approx. 8. In addition to ATP, GTP serves as a substrate, but CTP, ADP, AMP and p-nitrophenyl phosphate do not. Either Mg2+ or Mn2+ is required for activity and cannot be replaced by Ca2+ or Zn2+. The ATPase activity of goblet cell apical membranes is inhibited by neither the typical (Na+ + K+)-ATPase inhibitors, ouabain and orthovanadate, nor by the typical mitochondrial F1F0-ATPase inhibitors, azide and oligomycin. Although 1.5 microM DCCD is ineffective, 150 microM DCCD leads to total inhibition of ATPase activity. The ATPase activity of goblet cell apical membranes is stimulated not only by K+, but also, in order of decreasing effectiveness, by Rb+, Li+, Na+ and even Mg2+. Replacement of Cl- by Br-, F- and HCO3- has less influence than variation of the cations. However, replacement of Cl- by NO3- inhibits strongly this ATPase activity. The ATPase activity described above is characteristic of the alkali metal ion pump containing apical membranes of goblet cells and is not enhanced to a similar degree in other purified midgut epithelial cell plasma membrane segments. Its localization, its broad cation specificity and its insensitivity to ouabain all mimic properties of active ion transport by the lepidopteran midgut and suggest this ATPase as a possible key component of the lepidopteran electrogenic alkali metal ion pump.
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PMID:Cation-stimulated ATPase activity in purified plasma membranes from tobacco hornworm midgut. 293 79

Culturing of Trypanosoma cruzi in the presence of ethidium bromide (EB; 1.0-2.5 microM), for 5 days, affected the biogenesis of the Fo/F1-ATPase complex, presumably by EB interference with the expression of the putative Fo-sector subunits encoded by maxicircle DNA. In vitro, EB inhibited ATP hydrolysis by the Fo/F1-ATPase complex and also by soluble F1, the former preparation being the most strongly affected (EB I50, 250 microM). Analysis of EB effect at increasing MgATP concentrations, as well as combination of EB and p-chloromercuribenzoate inhibitions, indicated that the dye interacts with ATPase at sites other than the catalytic ones. No correlation was found between the in vitro inhibition of ATPase and EB effect on parasite growth.
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PMID:Effects of ethidium bromide on the mitochondrial adenosine triphosphatase from Trypanosoma cruzi. 294 Oct 19

Anion dependence of (Ca2+ + K+)-stimulated Mg2+-dependent transport ATPase and its phosphorylated intermediate have been characterized in both "intact" and "broken" vesicles from endoplasmic reticulum of rat pancreatic acinar cells using adenosine 5'-[gamma-32P] triphosphate ([gamma-32P]ATP). In intact vesicles (Ca2+ + K+)-Mg2+-ATPase activity was higher in the presence of Cl- or Br- as compared to NO3-, SCN-, cyclamate-, SO4(2-) or SO3(2-). Incorporation of 32P from [gamma-32P]ATP into the 100-kDa intermediate of this Ca2+ATPase was also higher in the presence of Cl-, Br-, NO3- or SCN- as compared to cyclamate-, SO4(2-) or SO3(2-). When the membrane permeability barrier to anions was abolished by breaking vesicle membrane with the detergent Triton X-100 (0.015%) (Ca2+ + K+)-Mg2+ATPase activity in the presence of weakly permeant anions, such as SO4(2-) and cyclamate-, increased to the level obtained with Cl-. However, 32P incorporation into 100-kDa protein was still higher in the presence of Cl- as compared to cyclamate-, indicating a direct effect of Cl- on the Ca2+ATPase molecule. The anion transport blocker 4,4-diisothiocyanostilbene-2,2-disulfonate (DIDS) inhibited (Ca2+ + K+)-Mg2+ATPase activity to about 10% of the Cl- stimulation level, irrespective of the sort of anions present in both intact and broken vesicles. This indicates a direct effect of DIDS on (Ca2+ + K+)-Mg2+ATPase. K+ ionophore valinomycin influenced (Ca2+ + K+)-Mg2+ATPase activity according to the actual K+ gradient: Ko+ greater than Ki+ caused inhibition, Ko+ less than Ki+ caused stimulation. From these results we conclude that Ca2+ transport into endoplasmic reticulum is coupled to ion movements which must occur to maintain electroneutrality.
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PMID:Anion dependence of Ca2+ transport and (Ca2+ + K+)-stimulated Mg2+-dependent transport ATPase in rat pancreatic endoplasmic reticulum. 295 52

The 110K-calmodulin complex isolated from intestinal microvilli is an ATPase consisting of one polypeptide chain of 110 kD in association with three to four calmodulin molecules. This complex is presumably the link between the actin filaments in the microvillar core and the surrounding cell membrane. To study its structural regions, we have partially cleaved the 110K-calmodulin complex with alpha-chymotrypsin; calmodulin remains essentially intact under the conditions used. As determined by 125I-calmodulin overlays, ion exchange chromatography, and actin-binding assays, a 90-kD digest fragment generated in EGTA remains associated with calmodulin. The 90K-calmodulin complex binds actin in an ATP-reversible manner and decorates actin filaments with an arrow-head appearance similar to that found after incubation of F-actin with the parent complex; binding occurs in either calcium- or EGTA-containing buffers. ATPase activity of the 90-kD digest closely resembles the parent complex. In calcium a digest mixture containing fragments of 78 kD, a group of three at approximately 40 kD, and a 32-kD fragment (78-kD digest mixture) is generated with alpha-chymotrypsin at a longer incubation time; no association of these fragments with calmodulin is observed. Time courses of digestions and cyanogen bromide cleavage indicate that the 78-kD fragment derives from the 90-kD peptide. The 78-kD mixture can also hydrolyze ATP. Furthermore, removal of the calmodulin by ion exchange chromatography from this 78-kD mixture had no effect on the ATPase activity of the digest, indicating that the ATPase activity resides on the 110-kD polypeptide. The 78 kD, two of the three fragments at approximately 40 kD, and the 32-kD fragments associate with F-actin in an ATP-reversible manner. Electron microscopy of actin filaments after incubation with the 78-kD digest mixture reveals coated filaments, although the prominent arrowhead appearance characteristic of the parent complex is not observed. These data indicate that calmodulin is not required either for the ATPase activity or the ATP-reversible binding of the 110K-calmodulin complex to F-actin. In addition, since all the fragments that bind F-actin do so in an ATP-reversible manner, the sites required for F-actin binding and ATP reversibility likely reside nearby.
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PMID:Mapping of the microvillar 110K-calmodulin complex: calmodulin-associated or -free fragments of the 110-kD polypeptide bind F-actin and retain ATPase activity. 296 11

Transverse tubule membranes isolated from rabbit fast skeletal muscle contain a very active Mg2+-ATPase (ATP phosphohydrolase, EC 3.6.1.3). This enzyme is very sensitive to inactivation by most detergents. However, after solubilization with either lysolecithin or digitonin, the Mg2+-ATPase can be purified in active form. Using a combination of selective solubilization followed by lectin affinity chromatography, ion-exchange chromatography, and native gel electrophoresis, the Mg2+-ATPase has been purified to near homogeneity. A prominent band with molecular mass of 105 kDa is observed when the purified protein is analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified 105-kDa Mg2+-ATPase protein is not structurally similar to the sarcoplasmic reticulum Ca2+-ATPase protein, as evidenced by very different cyanogen bromide peptide maps and amino acid compositions. The structural dissimilarities are complemented by functional differences observed between the Ca2+- and Mg2+-ATPases, including differential susceptibility to proteases, chemical modification reagents, and inactivation by fluorescein isothiocyanate and vanadate. All these data taken together demonstrate that the Mg2+-ATPase is a unique protein with little, if any, structural similarity to the sarcoplasmic reticulum Ca2+-ATPase or to other related enzymes such as mammalian kidney (Na,K)-ATPase or gastric mucosal (H,K)-ATPase.
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PMID:Purification and characterization of the Mg2+-ATPase from rabbit skeletal muscle transverse tubule. 297 Apr 63

Recently, we demonstrated that more beta-type myosin heavy chain (HC) was expressed in the overloaded atrium, and that there were 2 structurally different beta-type myosin heavy chains in the bovine heart. To determine the existence of the 2 beta-type HC in other animals and to clarify the characteristics of these beta-type HCs, we produced tricuspid regurgitation and pulmonary stenosis in the canine heart, and performed an immunological study using 3 monoclonal antibodies, 2 beta-type specific antibodies (HMC14 and 50) and 1 alpha-type specific antibody (CMA19). In an immunohistochemical study, serial cryostat sections revealed that some myofibers reacted with HMC50 (HC beta 2), but almost no fibers were labeled with HMC14 in the normal atrium. However, in overloaded atria, not only HC beta 2 but the HC, reacted with HMC14 (HC beta 1). By affinity chromatography, HC beta 2 was fractionated from normal atrial myosin using HMC50 and HC beta 1 was fractionated from overloaded atrial myosin using HMC14. These 2 HC beta's were subjected to digestion by alpha-chymotrypsin, staphylococcus aureus V8 protease, and cyanogen bromide, and proved to have different peptide fragments. In respect to enzymatic properties, the Ca2+-activated ATPase activities of HC beta 1 and beta 2 were almost the same but lower than that of HC alpha. We concluded that the isozymic transition of HC alpha to HC beta in the atrium was experimentally induced by hemodynamic overload and that HC beta 1, which was hardly recognized in the normal atrium but highly induced by overload, was structurally different from HC beta 2, as expressed in the normal atrium.
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PMID:Isolation and characterization of two beta-type cardiac myosin in the canine atrium. 297 92

The membrane potential of L1210 murine leukemia cells was assessed by use of the tritiated lipophilic cation probe triphenylmethylphosphonium bromide. The potassium equilibrium potential of the cells was found to be -71 +/- 7 mV. The resting membrane potential was partly dissipated by the protonophore m-chlorocarbonylcyanidephenylhydrazone (10 microM), but was unaffected by ouabain (1 mM) and apparently by the calcium ionophore A23187 (2.5 microM). Monensin (20 microM) caused a hyperpolarization which, since it was blocked by ouabain, was presumed to be brought about by activation of the Na+K+-ATPase via an elevated cytoplasmic Na+ concentration. Adriamycin at concentrations as high as 5 X 10(-4) M brought about no change in the resting potential of the cells. Also, cytotoxic concentrations of adriamycin, unlike ouabain, had no effect on rubidium-86 transport into L1210 cells, nor upon a monensin-induced increased in rubidium-86 uptake. The results suggest that although adriamycin is capable of interaction with the plasma membrane, and may exert its cytotoxicity at this locus, changes in ion flux mediated by Na+K+-ATPase or those capable of changing the membrane potential do not appear to be implicated in its mechanism of action.
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PMID:Investigations of the action of the antitumour drug adriamycin on tumour cell membrane functions--I. 298 49

In HeLa cells two different types of mutants resistant to the cardiac glycoside ouabain (OuaR mutants) or erythrophleum alkaloid cassaine (CasR mutants) have been obtained. One type of mutants resistant to these compounds (designated as group A) are highly resistant (between 50 and 2000-fold) to various cardiac glycosides and their genins such as ouabain, oleandrin, digitoxin, digitoxigenin, strophanthidin, convallatoxin, gitoxin, gitoxigenin, gitaloxin, bufalin, and digoxigenin, but exhibit no cross-resistance to SC4453, a digoxin analog which contains a pyridazine ring in place of the lactone ring in the C-17 position. The second type of mutants (group B) exhibit cross-resistance to all of the cardiac glycosides including SC4453, but their level of resistance is at least 5-10-fold less than that of group A mutants. Interestingly, both groups of mutants exhibited similar degree of cross-resistance towards digoxin and actodigin (AY22241), indicating some differences in their behavior from other cardiac glycosides. Both classes of mutants exhibit no cross-resistance to a wide variety of other structurally and functionally related compounds, e.g. sanguinarine nitrate, ethacrynic acid, penicillic acid, veratridine, harmaline hydrochloride, 5,5'-diphenylhydantoin, quindonium bromide, methyl quinolizinum bromide, estradiol 17 beta-acetate, 21-acetoxy-pregnenolone, vanadium pentoxide, digitonin, and adriamycin, indicating that the genetic lesions in both groups of mutants are specific for cardiac glycosides. This inference is supported by the observation that both group A and B mutants show reduced binding of [3H]ouabain. In group A mutants, a part of the Na+/K+-ATPase activity is highly resistant to inhibition by ouabain, indicating that the genetic lesion in these mutants directly affects Na+/K+-ATPase. In contrast, the Na+/K+-ATPase from the group B mutants showed similar resistance towards ouabain and SC4453 as observed for the parental HeLa cells, indicating that these mutants are affected in a cellular component, other than Na+/K+-ATPase, which is involved in the interaction of cardiac glycosides with the cells. The lack of cross-resistance of the group A mutants to SC4453 and normal sensitivity of their Na+/K+-ATPase to this compound provides strong evidence that the mechanism of interaction of SC4453 with Na+/K+-ATPase differs from that of other cardiac glycosides.
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PMID:Cross-resistance and biochemical studies with two classes of HeLa cell mutants resistant to cardiac glycosides. The unusual behavior of cardenolide SC4453. 298 35

Ethacrynic acid (EA) highly sensitive Mg2+-ATPase activity was demonstrated in rat brain microsomes. Marker enzyme studies suggested that the EA highly sensitive Mg2+-ATPase activity originated mainly from plasma membranes, and possibly from synaptic vesicles. Oligomycin did not affect the EA highly sensitive Mg2+-ATPase activity. Sulfhydryl reagents, such as N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid), and anion transport inhibitors, such as 4-acetamide-4'-isothiocyanostilbene-2,2'-disulfonic acid, 4,4'-diisothiocyano-stilbene-2,2'-disulfonic acid and 2,4-dinitro-1-fluorobenzene, completely inhibited the EA highly sensitive Mg2+-ATPase activity with apparent Ki values at 5, 5, 8, 8 and 10 microM respectively. Treatment of microsomes with ethylenediaminetetraacetic acid and ammonium sulfate increased the EA highly sensitive Mg2+ and Na+,K+-ATPase activities, but not EA less sensitive Mg2+- or HCO3-ATPase activity, 2- to 3-fold that in crude microsomes. Relative substrate specificities of ATP much greater than GTP greater than ITP greater than UTP, CTP, a Km for ATP at 0.77 mM, and an optimal pH at pH 7.4 were observed. Among the anions tested (Cl-, Br-, F-, HCO3-, I-, SCN-, NO3-), EA highly sensitive Mg2+-ATPase activity was stimulated significantly by Cl- and reduced by NO3-. These data suggest that a novel, plasma membrane-located and anion-sensitive Mg2+-ATPase activity exists in the brain.
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PMID:Novel microsomal anion-sensitive Mg2+-ATPase activity in rat brain. 298 56

Pinaverium bromide at concentrations below 10(-5) M did not inhibit calmodulin-dependent enzymes such as phosphodiesterase and the Ca transport ATPase of the plasma membrane. At higher concentrations the compound interacted with the stimulation of those enzymes by calmodulin and also inhibited the calmodulin-independent activity. A similar inhibitory action was observed for the NaK ATPase. It is concluded that the inhibitory action of pinaverium bromide on smooth muscle concentration at concentrations below 10(-5) M was due to its interaction with the voltage-dependent Ca channels and not to its interference with the calmodulin-dependent activation of the contractile proteins.
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PMID:Action of pinaverium bromide on calmodulin-regulated functions. 299 77


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