Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
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

Ca2+ binding to a sarcolemma-enriched membrane fraction from pig myocardium possessing an intrinsic cyclic AMP-dependent protein kinase occurs at several classes of low affinity binding sites and at two high affinity binding sites with binding constants of about 1.5-1.7x10(7) M-1 (0.3 nmole of Ca2+/mg protein) and 0.9-2.9x10(6) M-1 (0.8 nmole of Ca2+/mg protein). Ca2+ binding properties are not affected by verapamil and ouabain, whereas ruthenium red depresses Ca2+ binding at the low affinity binding sites and La3+ ions strongly reduce both low and high affinity Ca2+ binding. A profound inhibition of the high affinity Ca2+ binding sites was observed in the presence of Na+ ions, half-maximal inhibition at a free Ca2+ concentration of 2x10(-8) M being achieved by 11 mM NaC1. High affinity Ca2+ binding is also diminished after pretreatment of the membranes with trypsin and phospholipase A. Phosphorylation of one or two of the membrane proteins by the endogenous cyclic AMP-dependent protein kinase leads at both classes of high affinity Ca2+ binding sites to an approximately 4-fold increase in affinity, the number of these sites remaining unchanged. The high affinity Ca2+ binding sites may possibly be involved in Ca2+ extrusion from the cell and in the relaxation process.
 ...
PMID:Increased Ca2+ binding by a cardiac cell membrane preparation after cyclic AMP-enhanced intrinsic membrane protein phosphorylation. 17 98

The present study demonstrated the presence within the myocardium of phosphoprotein phosphatase activity which can account for dephosphorylation of a 22,000 dalton phosphoprotein of cardiac sarcoplasmic reticulum that has been associated with the stimulatory effects of adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase on calcium transport (Tada, M., Kirchberger, M. A., and Katz, A. M. (1975) J. Biol. Chem. 250:2640-2647). Dog cardiac microsomes, consisting mainly of fragmented sarcomplasmic reticulum, were phosphorylated by incubation with cyclic AMP-dependent protein kinase and [gamma-32P]ATP, and subsequently washed with trichloroacetic acid or buffered KCl. Phosphorylated microsomes contained approximately 1 nmole of 32P bound per mg of microsomal protein, 32P labeling occurring almost exclusively at the 22,000 dalton component. Soluble phosphoprotein phosphatases, isolated from the cytosol, catalyzed dephosphorylation of 32P-labeled microsomes. The existence of a phosphoprotein phosphatase that is associated with the microsomes was demonstrated by the ability of the microsomes to dephosphorylate 32P-histone. This membrane-associated phosphatase activity can also account for a rapid decrease in the amount of 32P-labeling of the 22,000 dalton protein. The dephosphorylation of the phosphorylated 22,000 dalton protein by phosphoprotein phosphatase satisfies an important requirement for the phosphorylation of the 22,000 dalton protein to serve a physiological role, namely, its reversibility.
 ...
PMID:Phosphoprotein phosphatase-catalyzed dephosphorylation of the 22,000 dalton phosphoprotein of cardiac sarcoplasmic reticulum. 17 94

Disulfide reductase (DSR) of mice liver supernatant is kinetically demonstrated as associating-dissociating oligomeric protein with positive homotropic cooperativity for the substrate. Cyclic 3',5'-AMP (10(-11)--10(-5) M) activates DSR and increases V, but does not change either [S]0,5, nor nH and does not shift the plot of specific activity versus the enzyme concentration. ATP, GTP, UTP, CTP, protamine, histone, Mg2+, Ca2+, EDTA (but not adenosine, 5'-AMP, 2'3'-AMP, ADP beef serum albumin) activated DSR. The effects of different modifiers are not summed up. Preincubation is essential for the action of the majority of the activators. Heating for 8 minutes at 55 degrees C desensitized completely DSR to all the modifiers without changing its catalytic activity, [S]0,5 and nH values. Possible mechanisms of activation of DSR, especially the involvement of protein kinase, are discussed.
 ...
PMID:[Kinetics and regulatory properties of the disulfide reductase enzyme from mouse liver]. 17 10

Sarcolemmal membranes isolated from guinea pig heart ventricles contained an ATP-dependent calcium-sequestering activity. Sarcolemmal calcium accumulation but not binding was enhanced by preincubation of membranes with exogenous protein kinase, with cyclic AMP, or with isoproterenol. Protein kinase (EC 2.7.1.37) increased the V of Ca2+ accumulation by sarcolemma without any significant effect on the affinity for Ca2+. The endogenous protein kinase activity present in isolated sarcolemma affected membrane phosphorylation. Cyclic AMP increased the endogenous kinase activity modestly, whereas histone increased it significantly. Exogenous protein kinase also catalyzed phosphorylation of these membranes. Endogenous and exogenous kinase-catalyzed phosphorylation of sarcolemma was hydroxylamine-insensitive. Ca2+-dependent ATPase (EC 3.6.1.3) (extra ATPase) activity of sarcolemma was also increased by protein kinase.
 ...
PMID:Stimulation of calcium accumulation in cardiac sarcolemma by protein kinase. 17 78

Changes in the pancreatic beta-cell concentrations of adenosine 3':5'-cyclic phosphate (cyclic AMP) may lead to changes in rates of insulin release, although little is known of the exact mechanism by which this nucleotide may influence the secretory process. Previous studies indicated that in the beta-cell, as in other mammalian cell types, the effects of cyclic AMP may be exerted by the activation of a cyclic AMP-dependent protein kinase, and we have attempted to identify possible substrates for this enzyme in beta-cells. Cyclic AMP stimulated the phosphorylation of specific non-nuclear protein substrates; this effect was observed both in intact cells preincubated with sodium [32P]phosphate to label intracellular ATP and in broken cell preparations incubated with [gamma-32P]ATP. The substrates for protein kinase in islets are unknown but as in other tissues might include microtubular protein and specific proteins of the granule and plasma membranes. In separate experiments cyclic AMP stimulated the efflux of calcium from an organelle-bound (probably mitochondrial) pool, and this may result in rapid changes of intracellular calcium distribution in the beta-cell; these might in turn play an important role in the regulation of secretion. These results suggest that cyclic AMP may directly affect cytosolic calcium concentrations in the beta-cell, as well as promoting the phosphorylation and activity of other components which may be necessary for the maintenance of adequate secretory responses.
 ...
PMID:The mode of action of adenosine 3':5'-cyclic phosphate in the regulation of insulin secretion. 18 Dec 22

1. Giant fibres of the barnacle Balanus nubilus have been used as a preparation for studying the mode of action of cAMP on sodium transport. 2. It is shown that a concentration of cAMP as low as 10(-6)M, when micro-injected, causes a sharp rise in the radio-Na efflux. Ouabain fails to reverse the cAMP effect. 3. The magnitude of the response of the Na efflux to cAMP is markedly reduced by pre-injecting 100 or 500 mM-EGTA solutions or by omitting Ca2+ from the bathing medium. Both together fail to bring about a greater reduction in the response. 4. The response to cAMP is greatly reduced by pre-injecting the protein inhibitor of Walsh and practically abolished by pre-injecting 500 mM-EGTA and soaking in Ca-free artificial sea water, ASW. 5. The Ca2+-independent component of the Na efflux which is also stimulated by cAMP is shown to involve Na for H exchange. The magnitude of this exchange is governed by external pH. 6. The Na efflux into Ca2+-free, Li+-ASW is shown to be markedly stimulated by injecting cAMP, an effect which is enhanced by reducing external pH. 7. The Na efflux at 0 degrees C is stimulated by injecting cAMP. This is shown to be related to activation of the protein kinase by cAMP and to depend on the presence of external Ca2+. 8 (i) Ethacrynic acid when injected reduces the ouabain-insensitive Na efflux into HEPES-Ca2+-free ASW at pH 6-3. These same fibres show a marked response to cAMP. (II) The ouabain-insensitive Na efflux into HCO3-, Ca2+-free ASW from fibres pre-treated with ethacrynic acid fails to respond to external acidification. This is interpreted as indicating that ethacrynic acid inactivates the CO2-sensitive adenyl cyclase system. These same fibres when injected with cAMP show a marked response. (iii) Stimulation of the ouabain-insensitive Na efflux into HCO-3, Ca2+-free ASW by external acidification is reversed by injecting ethacrynic acid. These fibres when injected with cAMP show a reduced response. 9. It is concluded that: (i) stimulation of the Na efflux by injected cAMP is mainly due to activation of cAMP-dependent protein kinase; (ii) the underlying exchange mechanism consists of Na:Ca and Na:H exchange. Interaction of Ca2+ with a phosphorylated membrane, thereby modifying permeability remains as a real possibility; (iii) the site of action of CO2 and ethacrynic acid is the adenyl cyclase system. 10. The implications of activation of the adenyl cyclase system by CO2 and Na:H exchange are briefly touched upon.
 ...
PMID:Mode of stimulation by adenosine 3':5'-cyclic monophosphate of the sodium efflux in barnacle muscle fibres. 18 61

One of the low molecular weight components of myosin, g2, was isolated by alkali treatment of myosin and was chemically modified with a spin label reagent, 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. The label on g2 showed a rather weakly immobilized ESR spectrum and it was clearly affected by Ca2+; the half-maximal change was at around pCa 4. The spin-labeled g2 was incorporated into myosin by exchange with the intrinsic g2 of myosin in 0.6 M KSCN or 4 M LiC1. The label on g2 became strongly immobilized on association with myosin. Under the conditions used, ESR spectral change due to Ca2+ occurred at two different concentration ranges, which were as low as pCa 8 and at around pCa 4. Phosphorylated g2 was isolated from myosin after the protein kinase [EC 2.1.1.37]-catalyzed phosphorylation of myosin and it was also modified with the maleimide label. Dephosphorylation of the phosphorylated g2 was performed using E. coli alkaline phosphatase [EC 3.1.3.1]. The effects of Ca2+ on the ESR spectra of phosphorylated and dephosphorylated g2 were investigated on the state associated with myosin. A change in the ESR spectrum from strongly immobilized to weakly immobilized states was observed with both g2 chains on the addition of Ca2+. However, the effective concentration ranges of Ca2+ were quite different; around pCa 4 for the phosphorylated g2 and around pCa 8 for the dephosphorylated g2. The results indicate that g2 undergoes a conformational change at physiological levels of Ca2+ sufficient to saturate troponin, but it does not do so after phosphorylation.
 ...
PMID:Ca2+-induced conformational changes of spin-labeled g2 chain bound to myosin and the effect of phosphorylation. 18 78

Vinblastine-isolated microtubule protein from chick embryonic muscles has an enzymatic activity which catalyzes the formation of phosphatidic acid from diglycerides and ATP. The pH optimum (6.4), sedimentation on sucrose gradients (Mr = 85 000), and sensitivity to ions of this diglyceride kinase activity are different to those of a similar enzymatic activity present in 150 000 X g supernatants of chick embryonic muscle homogenates, suggesting that it is a different species which is associated specifically with the microtubules. The reaction requires a divalent ion (e.g. 0.4 mM Mg2+ gives half-maximal stimulation), and GTP can replace ATP rather effectively, especially at nucleotide concentrations lower than 50 muM. The sedimentation of the diglyceride kinase on sucrose gradients coincides with that of the microtubules-associated protein kinase (Mr = 75 000); the heat-stability and sensivitity to proteolysis of both activities are also very similar. Stimulation of one reaction by the addition of the corresponding exogenous substrate does not impair the phosphorylation of the other, and no radioactivity is lost from phosphatidic acid or the protein moiety upon incubation of pre-labelled microtubules with a large excess of unlabelled ATP or GTP. In addition to diglyceride and protein kinase activities (0.2 and 0.3 nmol 32P-transferred X min-1 X mg-1 microtubular protein, respectively), microtubules also contain an associated ATPase (2.8 nmol X min-1 X mg-1), which requires either Mg2+ or Ca2+, can hydrolyze GTP quite effectively, and sediments with a molecular weight of 95000. The results obtained are discussed in connection with the possible relationships existing among these enzymatic activities, as well as their probable role in microtubular functions.
 ...
PMID:Diglyceride kinase activity of microtubules. Characterization and comparison with the protein kinase and ATPase activities associated with vinblastine-isolated tubulin of chick embryonic muscles. 18 51

The effect of cyclic AMP on Ca2+ uptake by rabbit heart microsomal vesicular fractions representing mainly fragments of either sarcoplasmic reticulum or sarcolemma was investigated in the presence and absence of soluble cardiac protein kinase and with microsomes prephosphorylated by cyclic AMP-dependent protein kinase. The acceleration of oxalate-promoted Ca2+ uptake by fragmented sarcoplasmic reticulum following cyclic AMP-dependent membrane protein phosphorylation, observed by other authors, was confirmed. In addition it was found that the acceleration was greatest at pH 7.2 and almost negligible at pH 6.0 and pH 7.8. A very marked increase in Ca2+ uptake by cyclic AMP-dependent membrane protein phosphorylation was observed in the presence of boric acid, a reversible inhibitor of Ca2+ uptake. In addition to the microsomal fraction thought to represent mainly fragments of the sarcoplasmic reticulum, the effect of protein kinase and cyclic AMP on Ca2+ uptake was investigated in a cardiac sarcolemma-enriched membrane fraction. Ca2+ uptake by sarcolemmal vesicles, unlike Ca2+ uptake by sarcoplasmic reticulum vesicles, was inhibited by low doses of digitoxin. The acceleration of oxalate-promoted Ca2+ uptake by cyclic AMP and soluble cardiac protein kinase, however, was quite similar to what was seen in preparations of fragmented sarcoplasmic reticulum, which suggests that it may reflect an acceleration of active Ca2+ transport across the myocardial cell surface membrane.
 ...
PMID:Stimulation of Ca2+ uptake by cyclic AMP and protein kinase in sarcoplasmic reticulum-rich and sarcolemma-rich microsomal fractions from rabbit heart. 18 62


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>