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)

In goldfish xanthophores, the formation of pigment aggregate requires: 1) that a pigment organelle (carotenoid droplet) protein p57 be in the unphosphorylated state; 2) that self-association of pigment organelles occur in a microtubule-independent manner; and 3) that pigment organelles via p57 associate with microtubules. In the fully aggregated state, the pigment organelles are completely stationary. Pigment dispersion is initiated by activation of a cAMP-dependent protein kinase, which phosphorylates p57 and allows pigment dispersion via an active process dependent on F-actin and a cytosolic factor. This factor is not an ATPase, and its function is unknown. However, its abundance in different tissues parallels secretory activity of the tissues, suggesting a similarity between secretion and pigment dispersion in xanthophores. The identity of the motor for pigment dispersion is unclear. Experimental results show that pigment organelles isolated from cells with dispersed pigment have associated actin and ATPase activity comparable to myosin ATPase. This ATPase is probably an organelle protein of relative molecular mass approximately 72,000, and unlikely to be an ion pump. Isolated pigment organelles without associated actin have 5x lower ATPase activity. Whether this organelle ATPase is the motor for pigment dispersion is under investigation. The process of pigment aggregation is poorly understood, with conflicting results for and against the involvement of intermediate filaments.
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PMID:Regulation of the distribution of carotenoid droplets in goldfish xanthophores and possible implication to secretory processes. 297 98

Studies were undertaken to determine whether factors which affect insulin secretion may exert their effects by altering the activity of an islet-cell plasma membrane Ca2+ extrusion pump. The insulin secretagogue, D-glucose, and a variety of phosphorylated hexoses, glucose 6-P, glucose 1,6-P, fructose 6-P, and fructose 2,6-P, were evaluated for their effect on an islet-cell plasma membrane (Ca2+ + Mg2+)-ATPase and were found to be ineffective in altering enzyme activity. D-Glucose also did not alter the rate of ATP-dependent Ca2+ uptake into plasma membrane vesicles. Similarly, cAMP, the catalytic subunit of cAMP-dependent protein kinase, arachidonic acid, or prostaglandin E2 did not affect either the plasma membrane (Ca2+ + Mg2+)-ATPase or the rate of ATP-dependent Ca2+ uptake into plasma membrane vesicles. Whereas previous studies have suggested that D-glucose and/or cAMP may inhibit ATPase activities in islets, these results indicate that the agents, i.e., D-glucose and cAMP, which stimulate and/or potentiate insulin secretion from the islet cell, do not modify Ca2+ fluxes by directly regulating the islet-cell plasma membrane (Ca2+ + Mg2+)-ATPase. In contrast, the acidic phospholipids, phosphatidic acid and phosphatidylserine, stimulated the enzyme activity in a concentration-dependent manner whereas phosphatidylcholine had only a minimal effect. The diacylglycerol, dilinolein, stimulated the (Ca2+ + Mg2+)-ATPase activity in the presence of phosphatidylserine, but not in the absence of phospholipids. These effects were independent of phospholipid-stimulated protein phosphorylation in the islet-cell plasma membrane under the conditions of the ATPase assay.
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PMID:Effect of insulin secretagogues and potential modulators of secretion on a plasma membrane (Ca2+ + Mg2+)-ATPase activity in islets of Langerhans. 298 94

Sarcolemmal membranes were isolated from porcine skeletal muscle by modifications of a LiBr-extraction technique. Latency determinations of acetylcholinesterase, ouabain-sensitive p-nitrophenylphosphatase, [3H]ouabain binding, and (Na+ + K+)-ATPase activities indicated that 65-76% of the membranes were sealed inside-out vesicles. The preparations were enriched in cholesterol and phospholipid, and demonstrated adenylate cyclase activity and both cAMP and cGMP phosphodiesterase activities. An indication of the purity of this fraction was that the Ca2+-ATPase activity (0.13 mumol Pi mg-1 min-1 at 37 degrees C) was 3.8% of that of porcine skeletal muscle sarcoplasmic reticulum preparations. Pertussis toxin specifically catalyzed the ADP-ribosylation of a Mr 41,000 sarcolemmal protein, indicating the presence of the inhibitory guanine nucleotide regulatory protein of adenylate cyclase, Ni. An endogenous ADP-ribosyltransferase activity, with several membrane protein substrates, was also demonstrated. The addition of exogenous cAMP-dependent protein kinase or calmodulin promoted the phosphorylation of a number of sarcolemmal proteins. The calmodulin-dependent phosphorylation exhibited an approximate K 1/2 for Ca2+ of 0.5 microM, and an approximate K 1/2 for calmodulin of 0.1 microM. 125I-Calmodulin affinity labeling of the sarcolemma, using dithiobis(succinimidyl propionate), demonstrated the presence of Mr 160,000 and 280,000 calmodulin-binding components in these membranes. These results demonstrate that this porcine preparation will be valuable in the study of skeletal muscle sarcolemmal ion transport, protein and hormonal receptors, and protein kinase-catalyzed phosphorylation.
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PMID:Components of purified sarcolemma from porcine skeletal muscle. 299 26

Contraction of tracheal smooth muscle requires the binding of Ca2+ to calmodulin, which then binds to and activates MLCK. The Ca2+-calmodulin-MLCK complex catalyzes the phosphorylation of myosin, which causes contraction by stimulating actin-activated Mg2+-ATPase activity of myosin. Myosin phosphorylation appears to be a transient event that is responsible for a high velocity of shortening. The mechanism responsible for maintenance of isometric force is unknown, although a second Ca2+-dependent mechanism with a greater sensitivity to Ca2+ than the activation of MLCK has been hypothesized. Force would be maintained through the slow cycling of nonphosphorylated cross-bridges or a small population of phosphorylated cross-bridges. Tracheal smooth muscle utilizes both extracellular and intracellular pools of Ca2+ for contraction. Moreover, the membrane channels through which extracellular Ca2+ passes have been subdivided into potential-dependent channels (PDCs) and receptor-operated channels (ROCs) independent of membrane potential. The relative extent to which extracellular and intracellular sources of Ca2+ as well as PDCs and ROCs are utilized depends on the agonist used for contraction, its concentration, and the type and location of the smooth muscle being investigated. Calcium antagonists such as verapamil and nifedipine, which reportedly block PDCs but not ROCs, are much better inhibitors of tracheal smooth muscle contractions induced by serotonin than those induced by acetylcholine, histamine, and leukotriene D4, indicating an effect of these latter three agents on ROCs. Relaxation of tracheal smooth muscle following stimulation of beta-adrenergic receptors most likely results from an increase in cAMP that stimulates a cAMP-dependent protein kinase to catalyze a protein phosphorylation that leads to relaxation by decreasing the intracellular concentration of Ca2+. The primary mechanisms whereby cAMP is thought to reduce intracellular Ca2+ to effect relaxation include: activation of a calmodulin-sensitive Ca2+ ATPase in the plasma and sarcoplasmic reticulum membranes, and extrusion of Ca2+ by a Na+-Ca2+ exchange mechanism coupled to Na+-K+-ATPase in the cell membrane. A more controversial mechanism for relaxation that bypasses Ca2+ might involve the dephosphorylation of myosin. Leukotrienes are released by various stimuli, including immunologic challenge, and have been considered as important mediators of bronchoconstriction in allergic asthma.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Tracheal smooth muscle. 301 93

Studies were conducted to investigate the molecular basis for bidirectional pigment granule transport in digitonin-lysed melanophores. Pigment granule dispersion, but not aggregation, required cAMP and resulted in the phosphorylation of a 57 kd polypeptide. cAMP-dependent protein kinase inhibitor prevented this phosphorylation as well as pigment dispersal. In contrast, both pigment aggregation and the concomitant dephosphorylation of the 57 kd polypeptide were blocked by phosphatase inhibitors. These data support a model in which pigment dispersion and aggregation require protein phosphorylation and dephosphorylation, respectively. Furthermore, studies using the ATP analog, ATP gamma S, suggest either that protein phosphorylation alone is sufficient for dispersion or that transport is mediated by a unique force-generating ATPase that can use ATP gamma S for hydrolyzable energy.
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PMID:Bidirectional pigment granule movements of melanophores are regulated by protein phosphorylation and dephosphorylation. 302 41

The composition and function of fetal and mature sheep cardiac sarcoplasmic reticulum membranes were investigated. Phospholamban, a major phosphoprotein in the mature sarcoplasmic reticulum membranes, was present in early stages of cardiac myogenesis. This fetal form of phospholamban was phosphorylated by cAMP-dependent protein kinase but not in the presence of Ca2+ and calmodulin. Ca2+ uptake and Ca2+-dependent ATPase activity were low in fetal sarcoplasmic reticulum compared with the adult controls, although the apparent affinities for Ca2+ were similar. Sarcoplasmic reticulum vesicles isolated at all developmental stages had very low levels of plasma membrane (as determined by Na+-K+-ATPase and Na+-Ca2+ exchanger activities) and mitochondrial contamination. Sarcoplasmic reticulum Ca2+ uptake and Ca2+-dependent ATPase activities were not affected by micromolar concentrations of vanadate, and the accumulated Ca2+ could not be released by the addition of NaCl. The amount of both the 110- and 55-kDa protein bands, identified with specific antibodies as Ca2+-ATPase and calsequestrin, respectively, was low in early stages of cardiac myogenesis. Age-related differences in the Ca2+ transport properties of cardiac sarcoplasmic reticulum and in the amount of the Ca2+-ATPase and calsequestrin may explain alterations in the regulation of intracellular Ca2+ concentrations in the fetal heart. This may contribute to the developmental changes in myocardial function.
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PMID:Differentiation of sarcoplasmic reticulum during cardiac myogenesis. 302 62

Sarcolemmal properties implicated in the skeletal muscle disorder, malignant hyperthermia (MH), were examined using sarcolemma-membrane vesicles isolated from normal and MH-susceptible (MHS) porcine skeletal muscle. MHS and normal sarcolemma did not differ in the distribution of the major proteins, cholesterol or phospholipid content, vesicle size and sidedness, (Na+ + K+)-ATPase activity, ouabain binding, or adenylate cyclase activity (total and isoproterenol sensitivity). The regulation of the initial rates of MHS and normal sarcolemmal ATP-dependent calcium transport (calcium uptake after 1 min) by Ca2+ (K1/2 = 0.64-0.81 microM), calmodulin, and cAMP-dependent protein kinase were similar. However, when sarcolemmal calcium content was measured at either 2 or 20 min after the initiation of active calcium transport, a significant difference between MHS and normal sarcolemmal calcium uptake became apparent, with MHS sarcolemma accumulating approximately 25% less calcium than normal sarcolemma. Calcium transport by MHS and normal sarcolemma, at 2 or 20 min, had a similar calmodulin dependence (C1/2 = 150 nM), and was stimulated to a similar extent by cAMP-dependent protein kinase or calmodulin. Halothane inhibited MHS and normal sarcolemmal active calcium uptake in a similar fashion (half-maximal inhibition at 10 mM halothane), while dantrolene (30 microM) and nitrendipine (1 microM) had little effect on either MHS or normal sarcolemmal calcium transport. After 20 min of ATP-supported calcium uptake, 2 mM EGTA plus 10 microM sodium orthovanadate were added to initiate sarcolemmal calcium efflux. Following an initial rapid phase of calcium release, an extended slow phase of calcium efflux (k = 0.012 min-1) was similar for both MHS and normal sarcolemma vesicles. We conclude that although a number of sarcolemmal properties, including passive calcium permeability, are normal in MH, a small but significant defect in MHS sarcolemmal ATP-dependent calcium transport may contribute to the abnormal calcium homeostasis and altered contractile properties of MHS skeletal muscle.
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PMID:Skeletal muscle sarcolemma in malignant hyperthermia: evidence for a defect in calcium regulation. 302 85

Congestive heart failure is a complex physiopathological state where both myocardial hypo-contraction and excessive peripheral vasoconstriction lead to lower cardiac output. The increase in cytosolic calcium concentration triggers the contractile processus. Digitalis inhibits the Na+/K+ ATPase enzyme and indirectly increases intracellular calcium concentration. beta 1 agonists increase the synthesis of cAMP-dependent protein kinase and hence the recruitment of new receptor-operated calcium channels which increase the calcium influx and the mobilization from its intracellular storage sites. Vascular smooth muscle contraction occurs with calcium influx into the cell resulting from various receptor activation. In congestive heart failure, activation of the sympathetic nervous system and of the renin-angiotensin system leads to neurohumoral-induced peripheral vasoconstriction. Renal effects of angiotensin II and aldosterone are responsible for sodium and water retention. alpha 1-blocking agents are drugs that block competitively the catecholamines effects on vascular receptors. Angiotensin I-converting-enzyme inhibitors block the formation of the key-element of the system: angiotensin II. Both alpha 1-blocking agents and converting-enzyme inhibitors show vasodilatator effects and acutely improve hemodynamic status of patients with congestive heart failure. Converting-enzyme inhibitors exhibit specific improvement of intrarenal hemodynamics and do not induced sodium and water retention in longterm therapy.
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PMID:[Pharmacological bases of the treatment of cardiac insufficiency]. 303 68

The Ca2+ ATPase of heart sarcolemma was stimulated by the exposure of sarcolemma vesicles to ATP and the catalytic subunit of the cAMP-dependent protein kinase. The effect of the phosphorylation system was primarily on the Km(Ca2+) of the pumping ATPase. The ATPase purified from heart sarcolemma or erythrocytes became phosphorylated under the conditions mentioned above. Hydroxylamine treatment of the labeled ATPase has shown that the phosphorylation was additive to be acylphosphate formed on the ATPase during the reaction cycle. The stoichiometry of the kinase-promoted phosphorylation (i.e. the fraction of the ATPase molecules that became labeled) approached 30% with both the heart and the erythrocyte enzyme.
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PMID:Phosphorylation of the Ca2+-pumping ATPase of heart sarcolemma and erythrocyte plasma membrane by the cAMP-dependent protein kinase. 316 Jul 6

Phospholamban, a putative regulator of the Ca2+-dependent ATPase of cardiac sarcoplasmic reticulum (SR), was purified from canine cardiac SR membranes. Cardiac SR was extracted with deoxycholate and fractionated with ammonium sulfate followed by gel permeation high performance liquid chromatography in the presence of the nonionic detergent, octa-ethylene glycol mono-n-dodecyl ether (C12E8), and KI. Further purification was achieved with CM-Sepharose CL 6B column chromatography in the presence of C12E8. The purified phospholamban showed a single band of 22,000 daltons on neutral sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (Weber, K., and Osborn, M. (1969) J. Biol. Chem. 244, 4406-4412) and 27,000 daltons on alkaline SDS gels (Laemmli, U. K. (1970) Nature (Lond.) 227, 680-685). Boiling of phospholamban in 2% SDS produced total conversion into the lower molecular weight component on SDS gels (11,000 on Laemmli gel and 10,500 on Weber and Osborn gel). The apparent molecular weight of phospholamban on SDS gels was slightly increased by cAMP-dependent phosphorylation. The extent of phosphorylation catalyzed by cAMP-dependent protein kinase in the purified phospholamban preparations was about 42 nmol of phosphate/mg of protein when the protein concentration was determined by the method of Lowry et al. (Lowry, O. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J. (1951) J. Biol. Chem. 193, 265-275), or 138 nmol/mg of protein based on the protein concentration estimated by the dye absorption method. Rabbit antisera were prepared against purified phospholamban. The obtained antisera were found to bind to purified phospholamban as well as that in cardiac SR. No reaction was detected in fast skeletal muscle SR by immunofluorescent staining of Western blots. The present preparation of purified phospholamban and the antisera should facilitate further understanding of the regulatory action of phospholamban on the calcium pump ATPase.
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PMID:Purification and characterization of phospholamban from canine cardiac sarcoplasmic reticulum. 388 14


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