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

A rat heart sarcolemmal preparation could be obtained in which both 5'-nucleotidase and adenylate cyclase were enriched approx. 9-fold by subjecting a homogenate to a discontinuous sucrose gradient, without the use of a high salt extraction. After incubation of this fraction with Mg[gamma-32P]ATP, the majority of 32P incorporated was present in 24 000- and 9000-dalton protein components. Only when a heart cytosol fraction or a purified cyclic AMP-dependent protein kinase was added, was enhancement of 32P-incorporaton found by addition of cyclic AMP. The 9000- and 24 000-dalton proteins appeared to be interconvertible. The degree of conversion could be affected by changing the temperature during solubilizaion of the membranes in SDS prior to electrophoresis. This suggested that the 24 000-dalton protein does not correspond to phospholamban, first identified by others in canine heart sarcoplasmic reticulum. Moreover, it could be excluded that the 24 000-dalton protein was derived from contaminating myofibrillar troponin I. When the sarcolemmal fraction was preincubated with Ca2+, Mg2+, ATP and oxalate, contaminating sarcoplasmic reticulum vesicles, loaded with calcium oxalate, settled to a greater density in the sucrose gradient. Membrane constituents other than those with enzymatic activity were monitored to confirm the separation between sarcolemmal and sarcoplasmic reticulum membranes: Coomassie blue staining material, sialic acid, cholesterol and phospholipid. The 24 000- and 9000-dalton proteins were equally distributed among the sarolemmal and sarcoplasmic reticulum fractions present in the sucrose gradient. However, the rate of 32P-incorporation in the presence of heart cytosol fraction was much slowr in the sarcoplasmic reticulum than in the sarcolemmal fraction.
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PMID:Phosphorylation of low molecular weight proteins in purified preparations of rat heart sarcolemma and sarcoplasmic reticulum. 625

In canine cardiac sarcoplasmic reticulum, adenosine 3',5'-monophosphate (cyclic AMP)-dependent protein kinase specifically phosphorylates two proteins, as seen by sodium dodecyl sulfate-slab gel electrophoresis and autoradiography. One protein has a molecular weight ranging between 22,000 and 24,000 daltons and has previously been identified and named phospholamban (Tada, M., Kirchberger, M.A. and Katz, A.M. (1975) J. Biol. Chem. 250, 2640-2647). The other protein that the 32P label incorporates into has a molecular weight of approximately 6000. Like the 22,000 dalton protein, the 6000 dalton protein has characteristics of phosphoester bonding. The time-dependent course of phosphorylation shows that initially the 32P label is incorporated more rapidly into the 22,000 dalton protein than the 6000 dalton protein, with both proteins reaching a steady-state level of phosphorylation after 10 min of incubation. When both protein kinase and cyclic AMP are eliminated from the incubation medium, both the 22,000 and the 6000 dalton protein are still phosphorylated, but only to about a quarter of the activity found when cyclic AMP and protein kinases are included in the incubation mixture. The addition of phosphodiesterase completely eliminates the phosphorylation of both proteins. Treating the microsomes with trypsin prevents subsequent phosphorylation of either protein. Phosphorylating the microsomes first, then treating with trypsin, renders both the 22,000 and the 6000 dalton proteins resistant to even prolonged trypsin attack. Unphosphorylated, both proteins are solubilized by a very low concentration of deoxycholate. After phosphorylation the proteins cannot be solubilized by deoxycholate. Phosphorylation appears to alter greatly the physical properties of these proteins. Control experiments exclude the possibility that a lipid is being phosphorylated. After phosphorylation the phosphorylated 22,000 dalton protein is separated from the 6000 dalton protein by proteolipid extraction. After first treating the microsomes with methanol, the 22,000 dalton protein is then soluble in acidified chloroform/methanol, while the 6000 dalton protein remains insoluble. The finding that both proteins have much different biochemical properties when phosphorylated than when not, may be relevant in how they regulate calcium transport in the sarcoplasmic reticulum.
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PMID:Adenosine 3',5'-monophosphate-dependent phosphorylation of a 6000 and a 22,000 dalton protein from cardiac sarcoplasmic reticulum. 625 12

Two endogenous protein kinase activities, cAMP-dependent and calmodulin-Ca2+-dependent, are associated with isolated cardiac sarcoplasmic reticulum (SR) vesicles. Both kinases phosphorylate an endogenous substrate of approximately 22,000 daltons (phospholamban). The phosphorylation of phospholamban by either the intrinsic or by exogenous cAMP-dependent protein kinase is found to be Ca2+-independent between 0.05 and 100 microM free Ca2+. Calmodulin-dependent phosphorylation, on the other hand, does not require cAMP and is absolutely dependent on the presence of free Ca2+ over a concentration range that corresponds to physiological levels (10(-7) to 10(-5) M). Phosphorylation of SR vesicles by both kinases is additive and the extent of saturation of the cAMP-specific sites has no effect on the degree of stimulation by calmodulin or its Ca2+-dependence. Trifluoperazine, an inhibitor of calmodulin, inhibits calmodulin-dependent phosphorylation without affecting cAMP-dependent phosphorylation, indicating the presence of two types of kinases. This is made further evident by the selectivity of each kinase for exogenous substrates. Whereas cAMP-dependent protein kinase appears to phosphorylate histone ILA (a basic protein) preferentially, calmodulin-dependent protein kinase prefers phosvitin (an acidic protein).
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PMID:Studies on phosphorylation of canine cardiac sarcoplasmic reticulum by calmodulin-dependent protein kinase. 627 7

Canine cardiac sarcoplasmic reticulum vesicles contain intrinsic cAMP-dependent and Ca2+ -calmodulin-dependent protein kinase (EC 2.7.1.37) activities and a common substrate, phospholamban, for these enzymes. Cyclic AMP-dependent protein kinase associated with sarcoplasmic reticulum membranes was solubilized with Triton X-100. Solubilization of the sarcoplasmic reticulum protein kinase did not affect its dependency on cAMP or its substrate specificity. The solubilized cAMP-dependent protein kinase was purified by DEAE-cellulose chromatography and was characterized as a type II enzyme on the basis of its elution at high ionic strength. DEAE-purified cAMP-dependent protein kinase exhibited no Ca2+ -calmodulin-dependent protein kinase activity. Cytosol from canine cardiac muscle cells, chromatographed on DEAE-cellulose under conditions identical to those used with sarcoplasmic reticulum, exhibited the presence of both type I and type II cAMP-dependent protein kinase isozymes. The properties of the DEAE-cellulose purified type II protein kinases from sarcoplasmic reticulum and cytosol were similar. We conclude that cardiac sarcoplasmic reticulum contains primarily type II cAMP-dependent protein kinase and this is probably the enzyme which phosphorylates sarcoplasmic reticulum in vivo and regulates Ca2+ transport.
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PMID:Characterization of cyclic 3':5'-amp-dependent protein kinase in sarcoplasmic reticulum and cytosol of canine myocardium. 629 89

Two substrate proteins for cAMP-dependent protein kinase detected in a rat heart sarcolemma preparation displayed molecular weights of 24,000 and 9000 in sodium dodecyl sulfate gels and were shown to be interconvertible. The 9000-dalton protein could readily be separated from other low molecular weight phosphoproteins (mol. wt. 14,000 and 7000) by the use of 15% polyacrylamide gels. In addition to an endogenous cAMP-dependent protein kinase the membrane preparation also contained a protein-phosphorylation system that required Ca2+ and calmodulin. It appeared that both 24,000- and 55,000-dalton proteins were substrates for the endogenous Ca2+- and calmodulin-dependent protein kinase. Contaminating sarcoplasmic reticulum vesicles, first loaded with calcium oxalate, could be separated from the enriched sarcolemma preparation by sucrose gradient centrifugation. The separation was confirmed by comparative analysis of 5'-nucleotidase, Na+ -Ca2+ antiporter, and (Ca2+ + Mg2+)-dependent ATPase activities and by determination of gel electrophoretic (phospho)protein composition, sialic acid, cholesterol, and phospholipid contents. The 24,000-dalton phosphoprotein complex was equally distributed between sarcolemmal and sarcoplasmic reticulum fractions, whereas the 55,000- and 7000-dalton proteins were predominantly found in the sarcolemmal fraction. The 24,000-dalton protein was most likely phospholamban, because no other phosphoprotein was found in the 20,000 molecular weight range.
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PMID:Phosphorylation of low-molecular-weight proteins in preparations of rat heart sarcolemma and sarcoplasmic reticulum. 630 73

The rate of calcium transport by sarcoplasmic reticulum vesicles from dog heart assayed at 25 degrees C, pH 7.0, in the presence of oxalate and a low free Ca2+ concentration (approx. 0.5 microM) was increased from 0.091 to 0.162 mumol . mg-1 . min-1 with 100 nM calmodulin, when the calcium-, calmodulin-dependent phosphorylation was carried out prior to the determination of calcium uptake in the presence of a higher concentration of free Ca2+ (preincubation with magnesium, ATP and 100 microM CaCl2; approx. 75 microM free Ca2+). Half-maximal activation of calcium uptake occurs under these conditions at 10-20 nM calmodulin. The rate of calcium-activated ATP hydrolysis by the Ca2+-, Mg2+-dependent transport ATPase of sarcoplasmic reticulum was increased by 100 nM calmodulin in parallel with the increase in calcium transport; calcium-independent ATP splitting was unaffected. The calcium-, calmodulin-dependent phosphorylation of sarcoplasmic reticulum, preincubated with approx. 75 microM Ca2+ and assayed at approx. 10 microM Ca2+ approaches maximally 3 nmol/mg protein, with a half-maximal activation at about 8 nM calmodulin; it is abolished by 0.5 mM trifluperazine. More than 90% of the incorporated [32P]phosphate is confined to a 9-11 kDa protein, which is also phosphorylated by the catalytic subunit of the cAMP-dependent protein kinase and most probably represents a subunit of phospholamban. The stimulatory effect of 100 nM calmodulin on the rate of calcium uptake assayed at 0.5 microM Ca2+ was smaller following preincubation of sarcoplasmic reticulum vesicles with calmodulin in the presence of approx. 75 microM Ca2+, but in the absence of ATP, and was associated with a significant degree of calmodulin-dependent phosphorylation. However, the stimulatory effect on calcium uptake and that on calmodulin-dependent phosphorylation were both absent after preincubation with calmodulin, without calcium and ATP, suggestive of a causal relationship between these processes.
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PMID:Calmodulin-dependent elevation of calcium transport associated with calmodulin-dependent phosphorylation in cardiac sarcoplasmic reticulum. 630 68

To elucidate the role of 22000-dalton protein phospholamban, a putative regulator of Ca2+-dependent ATPase of cardiac sarcoplasmic reticulum, we examined the relationship between cyclic AMP- and calmodulin-dependent phosphorylation of phospholamban and their effects on ATPase activity and calcium transport of cardiac sarcoplasmic reticulum. Cardiac microsomes were incubated with [gamma-32P]ATP or unlabeled ATP, catalytic subunit of cyclic AMP-dependent protein kinase and/or exogenous calmodulin, and subsequently assayed for ATPase activity and calcium uptake by cardiac sarcoplasmic reticulum. Cyclic AMP-dependent phosphorylation of phospholamban was independent of Ca2+, whereas calmodulin-dependent phosphorylation of phospholamban was dependent on Ca2+ within a range between 0.2 and 50 microM. Cyclic AMP- and calmodulin-dependent phosphorylation of phospholamban occurred independently; when both kinases were operative, the amounts of phosphorylation were additive. Under these conditions, the phosphoproteins formed by cyclic AMP- and calmodulin-dependent protein kinases electrophoretically migrated as 11000-dalton components when sodium dodecyl sulfate-solubilized phosphoproteins were boiled prior to polyacrylamide gel electrophoresis. The ATPase activity was stimulated by either cyclic AMP- or calmodulin-dependent phosphorylation of phospholamban at Ca2+ concentrations up to 2 microM. The extents of stimulation of ATPase activity were additive when both types of phosphorylation were functional. Calcium uptake was similarly augmented by cyclic AMP- and/or calmodulin-dependent phosphorylation of phospholamban. These results indicate that Ca2+-dependent ATPase and calcium transport of cardiac sarcoplasmic reticulum are regulated by phospholamban phosphorylation catalyzed by cyclic AMP- and calmodulin-dependent protein kinases, thus suggesting a dual role of phospholamban in active calcium transport.
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PMID:Effects of phospholamban phosphorylation catalyzed by adenosine 3':5'-monophosphate- and calmodulin-dependent protein kinases on calcium transport ATPase of cardiac sarcoplasmic reticulum. 631 Jan 31

The cAMP-dependent phosphorylation of proteins of both non-fractionated microsomes of the dog myocardium and phospholamban were studied in experimental myocardial infarction. In the presence of cAMP and exogenous protein kinase, the incorporation of 33P into microsomes and phospholamban of the affected muscle decreased as compared to that in the intact heart muscle. During infarction, partial degradation of phospholamban was observed. At the same time there was an increase in endogenous proteinase activity in microsomes of the affected muscle. The phosphorylation of phospholamban combined with its treatment by trypsin was investigated. The data indicate the correlation between the degree of phospholamban phosphorylation and its proteinase resistance in both the affected and intact myocardium.
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PMID:[Phosphorylation of phospholamban in experimental myocardial infarction and proteolysis stabilization during phosphorylation]. 631 10

Canine cardiac sarcoplasmic reticulum is phosphorylated by adenosine 3',5'-monophosphate (cAMP)-dependent and by Ca2+-calmodulin-dependent protein kinases on an Mr 22 000 protein called phospholamban. Both types of phosphorylation are associated with an increase in the initial rate of Ca2+ transport. Thus, phospholamban appears to be a regulator for the calcium pump in cardiac sarcoplasmic reticulum. However, there is conflicting evidence as to the degree of association of the Ca2+-ATPase with its regulator, phospholamban. In this study, we report that phospholamban does not copurify with a Ca2+-ATPase preparation of high specific activity. Although 32P-labeled phospholamban is solubilized in the same fraction as the Ca2+-ATPase from cardiac sarcoplasmic reticulum, it dissociates from the Ca2+ pump during subsequent purification steps. Our isolation procedure results in an increase of over 4-fold in the specific activity of the Ca2+-ATPase, but a decrease of 2.5-fold in the specific activity of 32Pi-phosphoester bonds (pmol Pi/mg). Furthermore, the purified Ca2+-ATPase enzyme preparation is not a substrate for protein kinase in vitro to any significant extent. These data indicate that phospholamban does not copurify with the Ca2+-ATPase from cardiac sarcoplasmic reticulum. Isolation of a Ca2+-ATPase preparation essentially free of phospholamban will aid in future kinetic studies designed to elucidate similarities and differences in the Ca2+-ATPase parameters from cardiac and skeletal muscle (which is known not to contain phospholamban).
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PMID:Phospholamban, the regulator of the cardiac sarcoplasmic reticulum calcium pump, does not copurify with the Ca2+-ATPase enzyme. 631 68

Stimulation of secretion in exocrine cells by agonists involving cAMP as second messenger is associated with the phosphorylation of a specific membrane-associated 22.4-kDa protein (protein III) (Jahn et al.). Here it is shown by subcellular fractionation of rat parotid gland lobules that protein III is associated with the endoplasmic reticulum. The submicrosomal fractions containing protein III, also contain the ATP-dependent microsomal calcium pump activity. Protein III in microsomal subfractions can be phosphorylated in vitro with catalytic subunit from cAMP-dependent protein kinase. Phosphorylated protein III contains exclusively P-serine. Protein III can be removed from ER-membranes with acid chloroform-methanol or Triton X-114, but not by high salt wash indicating that it is tightly associated with the membranes. Protein III is smaller than phospholamban and, in contrast to phospholamban, resistant to heating in SDS. A relationship between phosphorylation of protein III and microsomal calcium sequestration is discussed.
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PMID:Specific phosphorylation of a protein in calcium accumulating endoplasmic reticulum from rat parotid glands following stimulation by agonists involving cAMP as second messenger. 631 93


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