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)

The purpose of this investigation was to characterize the phosphorylation of bovine cardiac troponin by cyclic AMP-dependent protein kinase. The purified troponin-tropomyosin complex from beef heart contained 0.78 +/- 0.15 mol of phosphate per mol of protein. Analysis of the isolated protein components indicated that the endogenous phosphate was predominately in the inhibitory subunit (TN-I) and the tropomyosin-binding subunit (TN-T) of troponin. When cardiac troponin or the troponin-tropomyosin complex was incubated with cyclic AMP-dependent protein kinase and [gamma-32P]ATP, the rate of phosphorylation was stimulated by cyclic AMP and inhibited by the heat-stable protein inhibitor of cyclic AMP-dependent protein kinase. The 32P was incorporated specifically into the TN-I subunit with a maximal incorporation of 1 mol of phosphate per mol of protein. The maximal amount of phosphate incorporated did not vary significantly between troponin preparations that contained low or high amounts of endogenous phosphate. The Vmax of the initial rates of phosphorylation with troponin or troponin-tropomyosin as substrates was 3.5-fold greater than the value obtained with unfractionated histones. The rate or extent of phosphorylation was not altered by actin in the presence or absence of Ca2+. The maximal rate of phosphorylation occurred between pH 8.5 and 9.0. At pH 6.0 and 7.0 the maximal rates of phosphorylation were 13 and 45% of that observed at pH 8.5, respectively. These results indicate that cyclic AMP formation in cardiac muscle may be associated with the rapid and specific phosphorylation of the TN-I subunit of troponin. The presence of endogenous phosphate in TN-T and TN-I suggests that kinases other than cyclic AMP-dependent protein kinase may also phosphorylate troponin in vivo.
...
PMID:Phosphorylation of cardiac troponin by cyclic adenosine 3':5'-monophosphate-dependent protein kinase. 1 36

A protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) which catalyzes the phosphorylation of troponin T, phosvitin and casein has been purified over 2000 fold from rabbit skeletal muscle. The partial purification of this new enzyme, designated troponin T kinase, involves precipitation of contaminating proteins at pH 6.1, fractionation of the supernatant with (NH4)2SO4 and successive column chromatographies on DEAE-cellulose, hydroxyapatite and Sepharose 6B. The chromatographic patterns on DEAE-cellulose and hydroxyapatite columns show two peaks of troponin T kinase activity. Gel filtration experiments indicate the existence of multiple, possibly aggregated, forms of the enzyme. The purified enzyme does not catalyze the phosphorylation of phosphorylase b, troponin I, troponin C, tropomyosin, protamine, or myosin light chain 2 nor does it catalyze the interconversion of glycogen synthase I into the D form. Troponin T kinase is not affected by the addition of cyclic nucleotides or AMP to the reaction mixture. Divalent cations (other than Mg2+, required for the reaction) do not stimulate the enzyme, and several are inhibitory. Other characteristics of the reaction catalyzed by troponin T kinase, such as Km values for ATP and substrate proteins, pH optima, effect of the concentration of Mg2+, substitution of ATP for GTP have also been studied.
...
PMID:Purification and properties of troponin T kinase from rabbit skeletal muscle. 3 14

A bovine cardiac actin-tropomyosin-troponin complex was phosphorylated in the presence of [gamma-32P]ATP, Mg2+, adenosine 3',5'-monophosphate (cyclic AMP), and bovine cardiac cyclic-AMP-dependent protein kinase. Approximately 81% of the [32P]phosphate incorporated was identified as phosphoserine and phosphothreonine. Gel electrophoresis studies showed that 55% of the [32P]phosphate was associated with the inhibitory component of troponin (Tn-I) and 24% with a protein resembling the tropomyosin-binding component of troponin in the actin complex, respectively. The phosphorylation of Tn-I in the actin complex was inhibited 30% when Ca2+ was increased from 0.1 to 50 muM, but phosphorylation of other components was not affected by increasing Ca2+ concentration. Half-maximal calcium activation of the ATPase activity of reconstituted actomyosins made with the [32P]phosphorylated cardiac actin complex and cardiac myosin was shifted to Ca2+ values higher than those of actomyosins made with the nonphosphorylated actin complex.
...
PMID:Phosphorylation of a bovine cardiac actin complex. 15 2

1. Various proteins isolated from bovine tracheal smooth muscle were examined as phosphate acceptor substrates for a cyclic AMP-dependent protein kinase isolated from the same tissue. A fraction prepared in a manner similar to that of skeletal muscle troponin was the best substrate of the presumptive contractile proteins isolate. Actomyosin and tropomyosin were relatively poor substrates. 2. An assay was developed for the rapid detection in a large number of samples of the muscle specific substrate for the protein kinase on which we reported previously. 3. Using this assay, the muscle specific substrate found in bovine tracheal smooth muscle was partially purified resulting in a preparation which when resolved by polyacrylamide gel electrophoresis showed a single peak of 32P incorporated, and which could be further characterized. 4. Our findings suggest that the substrate contains a protein subunit of molecular weight 19 000, which can be phosphorylated at serine and threonine residues, in the presence of cyclic AMP and protein kinase. The phosphate is in a covalent ester linkage with these residues. 5. A phosphoprotein phosphatase was isolated from the bovine tracheal smooth muscle. 6. Bovine tracheal smooth muscle contains cyclic AMP dependent protein kinase and phosphoprotein phospahatase activity as well as the muscle specific substrate, suggesting that these elements may be part of a mechanism which regulates smooth muscle tone.
...
PMID:Cyclic AMP-stimulated phosphorylation of bovine tracheal smooth muscle contractile and non-contractile proteins. 18 31

Cardiac myofibrils were purified from canine myocardium, and the regulatory proteins (troponin + tropomyosin) were extracted and shown to contain endogenous cyclic AMP-dependent protein kinase activity. Other cyclic nucleotide stimulated the protein kinase activity but only at higher concentrations. The enzyme was able to catalyze phosphorylation of conventional substrates such as histones and casein as well as a component of the regulatory protein fraction with a molecular weight of 28,000 daltons. Endogenous phosphorylation required the presence of Mg2+ and was inhibited by Ca2+. A protein kinase inhibitor obtained from skeletal muscle inhibited the cyclicAMP-dependent phosphorylation. Escherichia coli alkaline phosphatase dephosphorylated the endogenous substrates. The level of phosphorylation found is severalfold higher than we have previously reported. A protein kinase, with its close association with the regulatory proteins, seems to be well suited to transmitting the message from the cyclic AMP to the regulatory proteins, a phenomenon that may influence the cardiac contractility via the troponin phosphorylation. The inhibitory effect of troponin on actomyosin might be changed by its state of phosphorylation.
...
PMID:Phosphorylation of cardiac regulatory proteins by cyclic AMP-dependent protein kinase. 18 66

A human skeletal actin.tropomyosin.troponin complex was phosphorylated in the presence of [gamma-32 P]ATP, Mg2+, adenosine 3':5'-monophosphate (cyclic AMP) and cyclic AMP-dependent protein kinase (protein kinase). Phosphorylation was not observed when the actin complex was incubated in the absence of protein kinase or 1 microM cyclic AMP. In the presence of 10(-7) M Ca2+ and protein kinase 0.1 mole of [32P]phosphate per 196 000 g of protein was incorporated. This was two-fold higher than the [32P]phosphate content of a rabbit skeletal actin complex but two-fold lower than that of a bovine cardiac actin complex. At high Ca2+, 5.10(-5) M, little change in the phosphorylation of a human skeletal actin complex occurred. Phosphoserine and phosphothreonine were identified in the [32P]phosphorylated actin complex. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed that 60% of the label was associated with the tropomyosin binding component of troponin. The inhibitory component of troponin contained 16% of the bound [32P]phosphate. Increasing the Ca2+ concentration did not significantly decrease the [32P]phosphate content of the phosphorylated proteins in the actin complex. No change in the distribution of phosphoserine or phosphothreonine was observed. Half maximal calcium activation of the ATPase activity of reconstitute human skeletal actomyosin made with the [32P] phosphorylated human skeletal actin complex was the same as a reconstituted actomyosin made with an actin complex incubated in the absence of protein kinase at low or high Ca2+.
...
PMID:Phosphorylation of an actin.tropomyosin.troponin complex from human skeletal muscle. 20 9

Toxin B from Clostridium difficile induces typical morphological changes of cultured cells consisting of rounding up and arborization, which are associated with a dramatic disruption of microfilaments. In this study, we show that toxin L, a cytotoxin produced by bacterial strain Clostridium sordellii, has similar effects on cultured cells including the redistribution of F-actin and of the adhesion plaque protein vinculin. It has been assumed that the mechanisms involved in cytopathic effects of toxin B are related to the function of an unidentified component that regulates the organization of the actin cytoskeleton. We demonstrate that the treatment of cultured astrocytes with toxin B or toxin L alters the incorporation of inorganic phosphate into several proteins. Immunoblot analysis revealed that one of these proteins is tropomyosin. Since tropomyosin stabilizes microfilaments and inhibits the severing activity of gelsolin, the toxin-induced phosphorylation may counteract this inhibition resulting in severing of microfilaments and capping of short filaments. A decrease in the radioactivity associated with intermediate filament protein vimentin was also detected using a monoclonal antibody which specifically recognizes a phosphorylated epitope of vimentin. Since vimentin is an in vivo substrate for various protein kinases, these data are in favor of broad effects of these toxins. Direct measurement of protein kinase C in cells exposed to toxin B or to toxin L did not reveal a significant change in protein kinase C activity. Furthermore, treatments with toxins do not increase cAMP levels, suggesting that toxins do not activate protein kinase A. Although further studies are required to determine the primary target site for the clostridial cytotoxin B and L, our results show that they provoke the alteration in the phosphorylation of cellular proteins.
...
PMID:Phosphorylation of cellular proteins in response to treatment with Clostridium difficile toxin B and Clostridium sordellii toxin L. 172 54

A hundred years after the first description, many aspects of pericytes remain to be examined. Mesenchymal in origin, pericytes form an incomplete envelopment around the endothelial cells and within the microvascular basement membrane of capillaries and postcapillary venules. Morphologically, they appear as long, slender, polymorphic cells, showing an elongated cell body, from which arise longitudinal and circumferential branches. Cell bodies and cytoplasmic processes of pericytes, as well as the endothelial cells, are enveloped by the same basal lamina, except for where they make direct contacts with each other. The pericyte/endothelial cell contacts are peg and socket, adhesion plaques and gap junctions, making up structural mechanisms for force transmission and a possible receptor system for cells, in which the pericyte and endothelial cells respond to secondary signals generated in the other cells. Electron microscopic studies have revealed an elaborate network of cytoplasmic filaments. Pericyte intermediate filament proteins show species and tissue differences, expressing vimentin or vimentin and desmin. The pericytes also express protein typical of contractile cells, i.e. smooth muscle-specific isoforms of actin and myosin, cyclic GMP-protein kinase and tropomyosin. A gradual transition is observed between pericytes and smooth muscle cells in both terminal arterioles and venules. Several general functions for the pericytes have been postulated: contractability; permeability regulator; integrity maintainer; endothelial cell growth modulator; and cell progenitor with considerable mesenchymal potential.
...
PMID:Microvascular pericytes: a review of their morphological and functional characteristics. 180 27

The contractile state of smooth muscle is regulated primarily by the sarcoplasmic (cytosolic) free Ca2+ concentration. A variety of stimuli that induce smooth muscle contraction (e.g., membrane depolarization, alpha-adrenergic and muscarinic agonists) trigger an increase in sarcoplasmic free [Ca2+] from resting levels of 120-270 to 500-700 nM. At the elevated [Ca2+], Ca2+ binds to calmodulin, the ubiquitous and multifunctional Ca(2+)-binding protein. The interaction of Ca2+ with CaM induces a conformational change in the Ca(2+)-binding protein with exposure of a site(s) of interaction with target proteins, the most important of which in the context of smooth muscle contraction is the enzyme myosin light chain kinase. The interaction of calmodulin with myosin light chain kinase results in activation of the kinase that catalyzes phosphorylation of myosin at serine-19 of each of the two 20-kDa light chains (native myosin is a hexamer composed of two heavy chains (230 kDa each) and two pairs of light chains (one pair of 20 kDa each and the other pair of 17 kDa each)). This simple phosphorylation reaction triggers cycling of myosin cross-bridges along actin filaments and the development of force. Relaxation of the muscle follows removal of Ca2+ from the sarcoplasm, whereupon calmodulin dissociates from myosin light chain kinase regenerating the inactive kinase; myosin is dephosphorylated by myosin light chain phosphatase(s), whereupon it dissociates and remains detached from the actin filament and the muscle relaxes. A substantial body of evidence has been accumulated in support of this central role of myosin phosphorylation-dephosphorylation in the regulation of smooth muscle contraction. However, a wide range of physiological and biochemical studies supports the existence of additional, secondary Ca(2+)-dependent mechanisms that can modulate or fine-tune the contractile state of the smooth muscle cell. Three such mechanisms have emerged: (i) the actin-, tropomyosin-, and calmodulin-binding protein, calponin; (ii) the actin-, myosin-, tropomyosin-, and calmodulin-binding protein, caldesmon; and (iii) the Ca(2+)- and phospholipid-dependent protein kinase (protein kinase C).
...
PMID:The Ayerst Award Lecture 1990. Calcium-dependent mechanisms of regulation of smooth muscle contraction. 181 84

The human trk oncogene (originally identified in a colon carcinoma) was activated by a genetic rearrangement which resulted in replacement of the extracellular ligand-binding domain of the proto-trk transmembrane receptor by non-muscle tropomyosin sequences. The product of the trk oncogene, a protein of 70 kDa (p70trk), possesses tyrosine-specific protein kinase activity, is autophosphorylated in vitro on tyrosine and is phosphorylated on serine, threonine and tyrosine residues in trk-transformed cells. By site-directed mutagenesis of trk oncogene cDNA, the codon for lysine (367) at the putative ATP-binding site was changed to that for methionine and the codons for tyrosines (503 and 504) at the putative autophosphorylation sites were changed to those for phenylalanine. Replacement of Lys-367 by methionine results in a biologically inactive, kinase-negative mutant. Phe-ala mutants of trk showed drastically reduced ability to induce morphologic transformation, anchorage-independent growth and tumorigenicity in mouse NIH3T3 cells and showed reduced in vitro tyrosine kinase activity when assayed by autophosphorylation and phosphorylation of histone as exogenous substrate. The present study indicates the role of these specific conserved residues in regulating the biochemical and biological properties of p70trk oncoprotein.
...
PMID:Mutational analysis of conserved residues in the tyrosine kinase domain of the human trk oncogene. 183 50


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

---