Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mechanism of protein kinase C (PKC) activation by phosphatidyl-L-serine (PS) is highly specific and occurs with high cooperativity [Lee, M.-H., & Bell, R. M. (1989) J. Biol. Chem. 264, 14797-14805]. To further investigate the multiplicity and specificity of PS cofactor requirement, some of the PS molecules present in Triton X-100 mixed micelles were substituted with nonactivating phospholipids devoid of required amino or carboxyl functional groups. The ability of these phospholipids to spare or reduce the mole percent of PS required was determined. Addition of phosphatidyl-(3-hydroxypropionate) (PP) or phosphatidate (PA) reduced the mole percent of PS required for maximal activity from 10 to 4 mol %, and also reduced the cooperativity of activation with PS. In contrast, phosphatidylethanolamine did not alter the dependence on PS. Phosphatidylethanol (P-Et) reduced the PS requirement to 2-4 mol % and cooperatively less efficiently than PP or PA. Phosphatidylglycerol and phosphatidylinositol resemble P-Et in their ability to reduce PS requirements and cooperativity. Therefore, it appears that the ability of phospholipids to substitute for PS in PKC activation depends on the negative charge in the phospholipid head group and the efficiency of substitution appears to be directly related to the negative charge density. The presence of two acyl groups within the phospholipid cofactor proved important since lyso-PS and lyso-PA replaced a portion of PS molecules required less efficiently than P-Et. Sodium oleate and sodium dodecyl sulfate behaved like lyso-PS. When other anionic lipids are present, approximately four molecules of PS per micelle are required for maximal PKC activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Supplementation of the phosphatidyl-L-serine requirement of protein kinase C with nonactivating phospholipids. 160 42

To examine the hypothesis that physical features of the membrane contribute to protein kinase C activation, phosphatidylcholine/phosphatidylserine/diolein (70:25:5) vesicles of defined acyl chain composition were tested for their ability to activate the enzyme. Maximal activation was found to correlate with the mole percent unsaturation in the system. Unsaturation could be provided by either the phosphatidylserine or the phosphatidylcholine component. Vesicles containing 5 mol% diolein but lacking any unsaturation in the phospholipid did not support activity, indicating that acidic head groups alone are not sufficient for activity. The saturated lipid vesicles could be rendered effective but only at very high (25 mol%) concentrations of diolein. The degree of acyl chain unsaturation and the positioning of the double bond had little effect on the activity, suggesting that the effect of the unsaturation is due to some physical property of the lipid rather than to a specific lipid-protein interaction. Addition of cholesterol to both saturated and unsaturated systems indicated that fluidity, as assessed by fluorescence anisotropy, did not correlate with activity. These results suggest that a physical property of the membrane other than fluidity is important for the activation of protein kinase C. A model for protein kinase C activation involving phase separation and/or head group spacing is discussed.
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PMID:Effect of phospholipid unsaturation on protein kinase C activation. 161 Aug 37

We have previously shown that 2,3-diphosphoglycerate (2,3-DPG) inhibits the phosphorylation of erythrocyte membrane cytoskeletal proteins by endogenous casein kinases. Here, we report that 2,3-DPG stimulates the phosphorylation of protein 4.1 by protein kinase C. Studies with red cell membrane preparations showed that while the phosphorylation of most of the membrane proteins by endogenous membrane-bound kinases and purified kinase C was inhibited by 2,3-DPG, the phosphorylation of protein 4.1 was slightly enhanced by the metabolite. The effect of 2,3-DPG was further examined using purified protein 4.1 preparations. Our results indicate that 2,3-DPG stimulates both the rate and the extent of phosphorylation of purified protein 4.1 by kinase C. The amount of phosphate incorporated was found to double to 2 mol of phosphate per mole of protein 4.1 in the presence of 10 mM 2,3-DPG. The increase in phosphorylation was distributed over all phosphorylation sites as revealed by an analysis of the labeling patterns of phosphopeptides resolved by high performance liquid chromatography, but a significantly higher incorporation was detected in two of the phosphopeptides. The stimulatory effect of 2,3-DPG on the phosphorylation of protein 4.1 was observed only with kinase C. Phosphorylation by the cytosolic erythrocyte casein kinase and the cyclic AMP-dependent protein kinase was inhibited by 2,3-DPG. Moreover, the stimulatory effect of 2,3-DPG seemed to be unique to the phosphorylation of protein 4.1 since a similar effect had not been observed with other protein kinase C substrates. Our results suggest that 2,3-DPG may play an important role in the regulation of cytoskeletal interactions.
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PMID:Effect of 2,3-diphosphoglycerate on the phosphorylation of protein 4.1 by protein kinase C. 165 67

There are clusters of basic amino acids on many cytoplasmic proteins that bind transiently to membranes (e.g., protein kinase C) as well as on the cytoplasmic domain of many intrinsic membrane proteins (e.g., glycophorin). To explore the possibility that these basic residues bind electrostatically to monovalent acidic lipids, we studied the binding of the peptides Lysn and Argn (n = 1-5) to bilayer membranes containing phosphatidylserine (PS) or phosphatidylglycerol (PG). We made electrophoretic mobility measurements using multilamellar vesicles, fluorescence and equilibrium binding measurements using large unilamellar vesicles, and surface potential measurements using monolayers. None of the peptides bound to vesicles formed from the zwitterionic lipid phosphatidylcholine (PC) but all bound to vesicles formed from PC/PS or PC/PG mixtures. None of the peptides exhibited specificity between PS and PG. Each lysine residue that was added to Lys2 decreased by one order of magnitude the concentration of peptide required to reverse the charge on the vesicle; equivalently it increased by one order of magnitude the binding affinity of the peptides for the PS vesicles. The simplest explanation is that each added lysine binds independently to a separate PS with a microscopic association constant of 10 M-1 or a free energy of approximately 1.4 kcal/mol. Similar, but not identical, results were obtained with the Argn peptides. A simple theoretical model combines the Gouy-Chapman theory (which accounts for the nonspecific electrostatic accumulation of the peptides in the aqueous diffuse double layer adjacent to the membrane) with mass action equations (which account for the binding of the peptides to greater than 1 PS). This model can account qualitatively for the dependence of binding on both the number of basic residues in the peptides and the mole fraction of PS in the membrane.
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PMID:Binding of peptides with basic residues to membranes containing acidic phospholipids. 188 32

Muscarinic acetylcholine receptors purified from porcine cerebrum were phosphorylated by protein kinase C purified from the same tissue. More than 1 mol of phosphate was incorporated per mole of receptor, with both serine and threonine residues being phosphorylated. Neither the degree nor the rate of the phosphorylation was affected by the presence or absence of acetylcholine. GTP-sensitive high-affinity binding with acetylcholine was observed for muscarinic receptors reconstituted with GTP-binding proteins (Gi or Go), irrespective of whether muscarinic receptors or the GTP-binding proteins had been phosphorylated by protein kinase C or not. This indicates that the interaction between purified muscarinic receptors and purified GTP-binding proteins in vitro is not affected by their phosphorylation.
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PMID:Phosphorylation by protein kinase C of the muscarinic acetylcholine receptor. 210 45

An inositol 1,4,5-trisphosphate 3-kinase purified from human platelets contains two major components, 53 and 36 kDa polypeptides. Each polypeptide expresses Ca2+/calmodulin-dependent enzymatic activity and is phosphorylated by an unidentified protein kinase in the enzyme preparation. The 36-kDa polypeptide may be further phosphorylated on serine residues by protein kinase C to a stoichiometry of 0.8 mole phosphate per mole of protein. Phosphorylation of the 36-kDa component is correlated with inhibition of the kinase activity; the inhibitory effect is dependent upon Ca2+ and phosphatidylserine/diolein and may be blocked by a selective peptide inhibitor of protein kinase C. Phosphorylation by protein kinase C decreases the Vmax of the enzyme from 160 to 28 nmol/mg/min; the Km (0.76 microM) is not altered. These data suggest that protein kinase C may negatively regulate inositol 1,4,5-trisphosphate 3-kinase activity in the human platelet.
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PMID:Phosphorylation by protein kinase C inactivates an inositol 1,4,5-trisphosphate 3-kinase purified from human platelets. 216 76

When smooth muscle calponin was incubated with protein kinase C, 1 mole of phosphate was incorporated per mole of calponin. The apparent Km value for calponin of the protein kinase was about 0.4 microM. The phosphorylation of calponin by protein kinase C was inhibited markedly by calmodulin in a calcium-dependent manner. Kinetic analysis of calmodulin-induced inhibition of calponin phosphorylation by protein kinase C revealed that calmodulin inhibited the phosphorylation in a noncompetitive fashion with calponin and the determined Ki value was 0.4 microM. These results suggest that interaction of calmodulin with calponin may play a regulatory role in the phosphorylation by protein kinase C and smooth muscle contraction.
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PMID:Modulation of smooth muscle calponin by protein kinase C and calmodulin. 222 54

The voltage-sensitive sodium channel from the electroplax of Electrophorus electricus is selectively phosphorylated by the catalytic subunit of cyclic-AMP-dependent protein kinase (protein kinase A) but not by protein kinase C. Under identical limiting conditions, the protein was phosphorylated 20% as rapidly as the synthetic model substrate kemptamide. A maximum of 1.7 +/- 0.6 equiv of phosphate is incorporated per mole. Phosphoamino acid analysis revealed labeled phosphoserine and phosphothreonine at a constant ratio of 3.3:1. Seven distinct phosphopeptides were identified among tryptic fragments prepared from radiolabeled, affinity-purified protein and resolved by HPLC. The three most rapidly labeled fragments were further purified and sequenced. Four phosphorylated amino acids were identified deriving from three consensus phosphorylation sites. These were serine 6, serine 7, and threonine 17 from the amino terminus and a residue within 47 amino acids of the carboxyl terminus, apparently serine 1776. The alpha-subunits of brain sodium channels, like the electroplax protein, are readily phosphorylated by protein kinase A. However, these are also phosphorylated by protein kinase C and exhibit a markedly different pattern of incorporation. Each of three brain alpha-subunits displays an approximately 200 amino acid segment between homologous repeat domains I and II, which is missing from the electroplax and skeletal muscle proteins [Noda et al. (1986) Nature (London) 320, 188; Kayano et al. (1988) FEBS Lett. 228, 1878; Trimmer et al. (1989) Neuron 3, 33]. Most of the phosphorylation of the brain proteins occurs on a cluster of consensus phosphorylation sites located in this segment. This contrasts with the pattern of highly active sites on the amino and carboxyl termini of the electroplax protein. The detection of seven labeled tryptic phosphopeptides compared to the maximal labeling stoichiometry of approximately 2 suggests that many of the acceptor sites on the protein may be blocked by endogenous phosphorylation.
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PMID:Identification of phosphorylation sites for adenosine 3',5'-cyclic phosphate dependent protein kinase on the voltage-sensitive sodium channel from Electrophorus electricus. 255 2

Protein kinase C (PKC), a calcium and phospholipid dependent protein kinase C, has emerged as a key element in signal transduction and cell regulation. It is activated by sn-1,2-diacylglycerol (DAG) second messengers and it serves as the receptor for phorbol esters, potent tumor promoters. PKC is now known to occur as a family of isoenzymes sharing similar structural features that allow regulation of activity by calcium, phospholipid, and DAG. In vitro mechanisms of PKC regulation by phospholipid, DAG, and phorbol esters have been studied using mixed micelles of Triton X-100/lipids. PKC activation occurs at physiologic mole fractions of phospholipid and DAG, does not require a bilayer, and appears to occur by a two-step mechanism whereby PKC initially interacts with a phospholipid surface and is then activated by the addition of DAG. Similar methodology has been used to explore the inhibition of PKC by different inhibitors that interact with its regulatory domain. Sphingosine and lysosphingolipids are potent inhibitors of PKC that prevent its interaction with DAG/phorbol esters. These naturally occurring metabolites have been shown to affect PKC activity in different cell systems. Disturbances in sphingolipid metabolism may lead to accumulation of lysosphingolipids with consequent inhibition of PKC. Additionally, these naturally occurring metabolites may have physiologic functions in regulating PKC activity by counteracting the action of DAG. The mechanism of action of sphingosine/lysosphingolipids and their possible physiologic function will be discussed.
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PMID:Regulation of protein kinase C by sphingosine and lysosphingolipids. 269 75

Protein kinase C catalyzes the incorporation of about 1.1, 0.7 and 0.4 mole of phosphate per mole of Lipocortin-I (P35), Lipocortin-II (P36) and Lipocortin-85 (P36 oligomer) respectively. The phosphorylation is specific for protein kinase C and is dependent on the presence of both calcium and phospholipids. While Lipocortin-I is phosphorylated on threonine residues, Lipocortin-II and Lipocortin-85 are phosphorylated on serine residues. The substoichiometric phosphorylation of Lipocortin-85 appears to preclude the potential regulation of this protein by protein kinase C. The phosphorylation of Lipocortin-I on threonine residues and Lipocortin-II on serine residues suggests these proteins may be regulated by distinct phosphorylation-dephosphorylation reactions.
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PMID:Phosphorylation of lipocortins in vitro by protein kinase C. 294 7


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