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

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A manyfold increase in phosphorylation of cardiac sarcoplasmic reticulum (SR) was seen when SR was incubated in the presence of a bovine cardiac cyclic AMP-dependent protein kinase and cyclic AMP. This phosphoprotein had stability characteristics of a phosphoester in which the phosphate is incorporated largely into serine, and its formation did not required calcium ions, unlike the formation of acyl phosphoprotein intermediate of calcium-transport ATPase which is present within the same membrane. When examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the protein kinase-catalyzed phosphorylation occurred at a 22,000-dalton component of the cardiac sarcoplasmic reticulum. This 22,000-dalton protein has been named "phospholamban" (lambda alpha mu beta alpha nu epsilon iota nu = to receive), based on its ability to receive phosphate from ATP. Phosphorylation of phospholamban by cyclic AMP-dependent protein kinase was associated with the stimulation of calcium transport by the cardiac sarcoplasmic reticulum. This stimulation was accompanied by an increase in the calcium-activated ATPase activity, indicating that the overall rate of calcium transport rather than its efficiency is enhanced by protein kinase. The 22,000-dalton phopholamban was susceptible to trypsin. Brief digestion with trypsin in the presence of 1 M sucrose prevented subsequent phosphorylation of phospholamban, while leaving the calcium pump apparently intact. Incubation of trypsin-treated sarcoplasmic reticulum with cyclic AMP-depentent protein kinase did not result in the stimulation of calcium transport. These results may suggest that phospholamban is a modulator of the calcium pump of the cardiac sarcoplasmic reticulum.
...
PMID:Regulation of calcium transport in cardiac sarcoplasmic reticulum by cyclic AMP-dependent protein kinase. 17 97

Cardiac microsomes were incubated with [gamma-32P]ATP and a cardiac adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase in the presence of ethylene glycol bis(bets-aminoethyl ether)-N,N'-tetraacetic acid. After solubilization in sodium dodecyl sulfate and fractionation by polyacrylamide gel electrophoresis, a single microsomal protein component of approximately 22,000 daltons was found to bind most of the 32P label. The 32P labeling of this component increased several fold when NaF was included in the incubation medium. No other component of cardiac microsomes, including sarcoplasmic reticulum ATPase protein, contained significant amounts of 32P label. This 22,000-dalton phosphoprotein formed by cyclic AMP-dependent protein kinase had stability characteristics of a phosphoester rather than an acyl phosphate. Washing of microsomes with buffered KCl did not decrease the amount of 32P labeling to the 22,000-dalton protein, suggesting that this protein is associated with the membranes of sarcoplasmic reticulum rather than being a contaminant from other soluble proteins. The 22,000-dalton protein was susceptible to trypsin. Brief digestion with trypsin in the presence of 1 M sucrose did not significantly affect microsomal calcium transport activity, but prevented both subsequent phosphorylation of the 22,000-dalton protein and stimulation of calcium uptake by cyclic AMP-dependent protein kinase, suggesting that this protein is a modulator of the calcium pump. These results are consistent with previous findings (Kirchberger, M.A., Tada, M., and Katz, A.M. (1974) J. Biol. Chem. 249, 6166-6173; Tada, M., Kirchberger, M.A., Repke, D.I., and Katz, A.M. (1974) J. Biol. Chem. 249, 6174-6180) that cyclic AMP-dependent protein kinase-catalyzed phosphorylation is associated with stimulation of calcium transport in the cardiac sarcoplasmic reticulum, and further indicate that this phosphorylation occurs at a component of low mass (22,000 daltons) of the cardiac sarcoplasmic reticulum which, while separable from the calcium transport ATPase protein (100,000 daltons) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, has the ability to regulate calcium transport by the cardiac sarcoplasmic reticulum.
...
PMID:Phosphorylation of a 22,000-dalton component of the cardiac sarcoplasmic reticulum by adenosine 3':5'-monophosphate-dependent protein kinase. 23 23

Canine cardiac sarcoplasmic reticulum is phosphorylated by an endogenous calcium X calmodulin-dependent protein kinase and phosphorylation occurs mainly on a 27 kDa proteolipid, called phospholamban. To determine whether this phosphorylation has any effect on Ca2+ release, sarcoplasmic reticulum vesicles were phosphorylated by the calcium X calmodulin-dependent protein kinase, while non-phosphorylated vesicles were preincubated under identical conditions but in the absence of ATP to avoid phosphorylation. Both non-phosphorylated and phosphorylated vesicles were centrifuged to remove calmodulin, and subsequently used for Ca2+ release studies. Calcium loading was carried out either by the active calcium pump or by incubation with high (5 mM) calcium for longer periods. Phosphorylation of sarcoplasmic reticulum by calcium X calmodulin-dependent protein kinase had no appreciable effect on the initial rates of Ca2+ released from cardiac sarcoplasmic reticulum vesicles loaded under passive conditions and on the apparent 45Ca2+-40Ca2+ exchange from cardiac sarcoplasmic reticulum vesicles loaded under active conditions. Thus, it appears that calcium X calmodulin-dependent protein kinase mediated phosphorylation of cardiac sarcoplasmic reticulum is not involved in the regulation of Ca2+ release and 45Ca2+-40Ca2+ exchange.
...
PMID:Lack of effects of calcium X calmodulin-dependent phosphorylation on Ca2+ release from cardiac sarcoplasmic reticulum. 244 73

Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in canine cardiac microsomes were found to be stimulated by heparin and various other polyanions. Prior treatment of the microsomes with the ionophores alamethicin or A23187 produced no change in the extent of stimulation of the ATPase activity by heparin yet eliminated net calcium uptake. This finding and a lack of change in the stoichiometric ratio of mol of calcium transported/mol of ATP hydrolyzed (calcium:ATP) suggest that the effect of heparin is on the calcium pump rather than on a parallel calcium efflux pathway. Certain polycationic compounds including poly-L-arginine and histone inhibited both cardiac and fast skeletal muscle microsomal calcium uptake and also produced no change in the stoichiometric ratio of calcium to ATP. Several lines of evidence indicate that the polyanionic compounds tested stimulate calcium uptake by interacting with phospholamban, the putative phosphorylatable regulator of the cardiac sarcoplasmic reticulum calcium pump, whereas polycationic compounds appear to interact with the pump. (i) Heparin stimulated calcium uptake to the same extent as protein kinase A or trypsin, whereas prior phosphorylation or tryptic cleavage of phospholamban from the membrane abolished the stimulatory effect of heparin. (ii) Calcium uptake and (Ca2+ + Mg2+)-ATPase activity in fast skeletal muscle microsomes, which lack phospholamban, were unaffected by heparin. (iii) Purified cardiac (Ca2+ + Mg2+)-ATPase activity was no longer stimulated by heparin yet was still inhibited by polycationic compounds. The heparin-induced stimulation of calcium uptake was dependent on the pH and ionic strength of the heparin-containing preincubation medium, hence electrostatic interactions appear to play a significant role in heparin's stimulatory action. The data are consistent with an inhibitory role of the positively charged cytoplasmic domain of phospholamban with respect to calcium pump activity and the relief of the inhibition upon reduction in phospholamban's positive charge by phosphorylation or binding of polyanions.
...
PMID:Modulation by polyelectrolytes of canine cardiac microsomal calcium uptake and the possible relationship to phospholamban. 247 44

Three systems mediate the fluxes of calcium across heart sarcolemma: the slow calcium channel (influx), the ATP-dependent calcium pump (efflux), and the Na+/Ca2+ exchanger (efflux, but possibly also influx). Calmodulin regulates the pumping ATPase by direct interaction and also by activating a protein kinase. The Na+/Ca2+ exchanger is modulated by calmodulin via a phosphorylation-dephosphorylation cycle. Both the kinase and the phosphatase are membrane-bound and calmodulin-sensitive. The kinase has higher Ca2+ affinity than the phosphatase.
...
PMID:Calmodulin in the regulation of calcium fluxes in cardiac sarcolemma. 257 85

The role of the plasma membrane in the regulation of lens fiber cell cytosolic Ca2+ concentration has been examined using a vesicular preparation derived from calf lenses. Calcium accumulation by these vesicles was ATP dependent, and was releasable by the ionophore A23187, indicating that calcium was transported into a vesicular space. Calcium accumulation was stimulated by Ca2+ (K1/2 = 0.08 microM Ca2+) potassium (maximally at 50 mM K+), and cAMP-dependent protein kinase; it was inhibited by both vanadate (IC50 = 5 microM) and the calmodulin inhibitor R24571 (IC50 = 5 microM), indicating that this pump was plasma-membrane derived and likely calmodulin dependent. Valinomycin, in the presence of K+, stimulated calcium uptake, suggesting that the calcium pump either countertransports K+, or is regulated in an electrogenic fashion. Inhibition of calcium uptake by selenite and p-chloromercuribenzoate demonstrates the presence of an essential -SH group(s) in this enzyme. Calcium release from calcium-filled lens vesicles was enhanced by Na+, demonstrating that these vesicles also contain a Na:Ca exchange carrier. p-Chloromercuribenzoate and p-chloromercuribenzoate sulfonic acid also promoted calcium release from calcium-filled vesicles, suggesting that this release, like calcium uptake, is in part mediated by a cysteine-containing protein. We conclude that lens fiber cell cytosolic Ca2+ concentration could be regulated by a number of plasma membrane processes. The sensitivity of both calcium uptake and release to -SH reagents has implications in lens cataract formation, where oxidation of lens proteins has been proposed to account for the elevated cytosolic Ca2+ in this condition.
...
PMID:Calcium regulation by lens plasma membrane vesicles. 284 Aug 57

Phospholamban, the putative regulator for the calcium pump, was purified to apparent homogeneity and in high yields from canine cardiac sarcoplasmic reticulum membranes. Purified phospholamban migrated with an apparent Mr of 27,000 in alkaline sodium dodecyl sulfate-polyacrylamide gels, and upon boiling in 7.5% sodium dodecyl sulfate, it dissociated into a lower molecular weight component of 5500-6000. Purified phospholamban contained 0.62 +/- 0.09 mumol of lipid Pi/mg of protein, and the major phospholipids were phosphatidylserine (34%), phosphatidylcholine (22%), sphingomyelin (17%), phosphatidylinositol (13%), and phosphatidylethanolamine (9%). Phospholamban was phosphorylated by cAMP-dependent protein kinase to a level of 207 nmol of Pi/mg, and this would indicate an incorporation of 1 mol of phosphate/mol of protein, assuming a molecular weight of 5500 for phospholamban. Phosphorylation of phospholamban could be reversed by a "phospholamban phosphatase" isolated from canine cardiac cytosol. Phospholipids associated with the purified phospholamban were also phosphorylated in the presence of the catalytic subunit of cAMP-dependent protein kinase, and the maximal phosphate incorporation was 4 nmol/mg of protein. The main phospholipids phosphorylated were phosphatidylinositol 4-monophosphate and phosphatidylinositol 4,5-bisphosphate. Phosphorylation of phospholipids was inhibited by the heat-stable inhibitor protein of the cAMP-dependent protein kinase, and it could be also reversed by the phospholamban phosphatase.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Phosphorylation and dephosphorylation of purified phospholamban and associated phosphatidylinositides. 284 74

Canine cardiac sarcoplasmic reticulum is phosphorylated by an endogenous calcium-calmodulin-dependent protein kinase on a 22,000 proteolipid, called phospholamban. Phosphorylation by the calcium-calmodulin-dependent protein kinase is associated with stimulation of the initial rates of calcium transport (Davis, B. A., Schwartz, A., Samaha, F. J., and Kranias, E. G. (1983) J. Biol. Chem. 258, 13587-13591). The present study shows that protein phosphatase activity, associated with canine cardiac sarcoplasmic reticulum vesicles, can catalyze dephosphorylation of the calcium-calmodulin-dependent sites on phospholamban. The activity was maximally stimulated by manganese; fluoride was inhibitory, but its effect was reversible. Dephosphorylation of phospholamban, which was prephosphorylated by calcium-calmodulin-dependent protein kinase, resulted in a reduction of the stimulation on calcium transport rates, particularly at submaximal calcium concentrations. The decrease in calcium transport was associated with a statistically significant decrease in the apparent affinity (EC50) for calcium. Rephosphorylation of phospholamban by the endogenous calcium-calmodulin-dependent protein kinase caused full recovery of the stimulation on calcium transport rates and reversal of the effects mediated by the protein phosphatase. Thus, the calcium pump in cardiac sarcoplasmic reticulum appears to be under reversible regulation mediated by endogenous calcium-calmodulin-dependent protein kinase and protein phosphatase. Such regulation may represent an important control mechanism for the myocardium.
...
PMID:Regulation of calcium transport by protein phosphatase activity associated with cardiac sarcoplasmic reticulum. 299 98

The calcium uptake and release machinery in heart SR have been characterized: (1) The calcium pump membrane is involved in energized Ca2+ uptake enabling muscle to relax. The calcium pump protein (CPP) in heart SR is modulated by protein kinase phosphorylation of phospholamban lowering the KCa2+. We conclude that in the membrane, phospholamban elevates KCa2+ of calcium pump protein. Phosphorylation of phospholamban attenuates the influence of phospholamban. In the limit, the intrinsic KCa2+ of calcium pump protein in heart and skeletal muscle are approximately the same. (2) The junctional face membrane is involved in calcium release which triggers muscle contraction. Ryanodine is a specific modulator of the Ca2+ release channels of SR which are involved in excitation-contraction coupling. The ryanodine receptor has been isolated, found to be equivalent to the feet structures, and on reconstitution into bilayers, identified as the calcium release channel of SR. The calcium release channel of SR is closed by ruthenium red and Mg2+ and opened by Ca2+ and ATP and low ryanodine concentration. The calcium release channel of SR is not effected by drugs such as nitrendipine, diltiazem and D-600 which modulate the slow inward Ca2+ channel of the plasmalemma/transverse tubule. (3) The calcium release channels from heart and skeletal muscle SR are similar but not identical (Table IV). Important differences distinguish the calcium release machinery in heart from that of skeletal muscle. 1. In heart there are two sources of calcium fluxes: a) extracellular Ca2+ enters via the plasmalemma slow inward calcium current; and b) "Ca2+ induced Ca2+ release" from SR. In skeletal muscle, SR is the single main source of calcium which enters via "Depolarization induced calcium release". 2. The calcium release channel from heart SR has a lower Mr approximately 340,000 vs 360,000 for skeletal muscle. 3. Ryanodine binding in cardiac SR is distinct from that in skeletal muscle (Fig. 7). 4. The isolated calcium release channel from heart SR is more sensitive to Ca2+ for calcium release (Hymel et al. 1988c). Significant progress has been achieved in identifying the calcium release channel of SR in heart and skeletal muscle. The focus of excitation-contraction coupling now shifts to defining the precise nature of the coupling of excitation to contraction.
...
PMID:Regulation of muscle contraction and relaxation in heart. 304 48

The effect of cAMP-dependent protein kinase on calcium uptake and protein phosphorylation in bovine aortic microsomes was examined. Acid gel electrophoresis demonstrated that the aortic microsomes contained a Ca2+-dependent, hydroxylamine-sensitive phosphoenzyme (Mr 110 kDa), characteristic of the calcium pump in sarcoplasmic reticulum, but showed no evidence of a sarcolemmal calcium pump. Calcium uptake by these aortic vesicles was markedly stimulated by oxalate, whereas calcium uptake by canine cardiac sarcolemmal vesicles was oxalate-independent. Both cAMP plus protein kinase (cAMP-PK) and catalytic subunit of protein kinase stimulated oxalate-supported calcium uptake by bovine aortic microsomes 23 +/- 3% (P less than 0.05) at 0.3 microM Ca2+, but had no effect at 6 to 10 microM Ca2+. Catalytic subunit of protein kinase and cAMP-PK phosphorylated an 11 kDa protein in bovine aortic microsomes which comigrated with canine cardiac phospholamban after boiling in sodium dodecylsulfate. The stoichiometry of the aortic 11 kDa phosphoprotein to 110 kDa phosphoenzyme was approximately 1:1. These data are consistent with the recent identification of phospholamban in various smooth muscles, and suggest that cAMP-mediated vascular relaxation may in part be attributable to stimulation of calcium uptake by the sarcoplasmic reticulum.
...
PMID:Regulation of calcium uptake in bovine aortic sarcoplasmic reticulum by cyclic AMP-dependent protein kinase. 322 9


1 2 3 4 5 6 Next >>

---