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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Proline-directed protein kinase (PDPK), a complex of p34cdc2 and p58cyclin A, phosphorylates bovine neurofilaments (NFs) in vitro. Incubation of intact filaments with PDPK led to strong labeling of the heavy (NF-H) and middle (NF-M) molecular weight NF proteins and weaker labeling of the low molecular weight protein (NF-L). All three proteins were phosphorylated in solution, with the best substrate being NF-H. Proteins that had been dephosphorylated by enzymatic treatment were better substrates than native proteins--as many as 6 mol of phosphate were incorporated per mole of NF-H. Partial proteolytic cleavage experiments combined with two-dimensional peptide mapping indicated that NF-H and NF-M were phosphorylated predominantly in the tail domains, with some phosphate also appearing in the heads. Soluble NF-L is phosphorylated on the head domain peptide L-3, whereas NF-L within intact filaments is phosphorylated only on the tail domain peptide L-1. Phosphorylation does not lead to filament disassembly. A possible role for PDPK in NF phosphorylation in vivo is discussed.
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PMID:Proline-directed protein kinase (p34cdc2/p58cyclin A) phosphorylates bovine neurofilaments. 154 71

To assess the possible functional role of single-strand DNA-binding (SSB) proteins in eucaryotic cell, a comparative study was made of SSB-proteins isolated from chromatin and the nonchromatin fractions of Ehrlich ascites tumour (EAT) cells. No appreciable differences between the two groups could be found either in SDS-gel electrophoretic patterns or in the ssDNA-binding capacity and stimulation of DNA replication in permeable EAT cells. However, the chromatin SSB-proteins incorporated 1.4-times more labelled phosphate in vivo; phosphate assays in the isolated chromatin and nonchromatin SSB-proteins yielded ca. 3 and 2 moles Pi/mole protein, respectively. Both preparations could be further phosphorylated in vitro with Ca-phospholipid-dependent protein kinase and the catalytic subunit of cAMP-dependent protein kinase, but the non-chromatin proteins were phosphorylated to a greater degree. In parallel with phosphorylation, the SSB-proteins displayed stronger binding to ssDNA cellulose. Phosphorylation may thus be a means of regulating the functions of SSB-proteins, in particular their interaction with chromatin.
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PMID:Properties of single-stranded DNA-binding proteins (SSB-proteins) from chromatin and nonchromatin fractions of Ehrlich ascites tumour: phosphorylation enhances the affinity of SSB-proteins for single-stranded DNA. 159 12

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

The activating factor of ATP.Mg-dependent protein phosphatase (FA) has been identified in brain microtubules. When using purified MAP-2 (microtubule associated protein 2) and tau proteins as substrates, FA could phosphorylate MAP-2 to 16 moles of phosphates per mole of protein with a Km value of 0.4 microM, and tau proteins to 4 moles of phosphates per mole of proteins with a Km value of about 3 microM. When using microtubules as substrates, FA could enhance many-fold the endogenous phosphorylation of many microtubule-associated proteins including MAP-2, tau proteins, and several low-molecular-weight MAPs. In contrast to other reported MAP kinases, such as cAMP-dependent protein kinase and Ca+2/phospholipid-dependent protein kinase, the FA-catalyzed phosphorylation of tau proteins could cause an electrophoretic mobility shift on sodium dodecyl sulfate polyacrylamide gel electrophoresis, suggesting that a dramatic conformational change of tau proteins was produced by FA. Peptide mapping analysis of the phosphopeptides derived from SV8 protease digestion revealed that FA could phosphorylate MAP-2 and tau proteins on at least four specific sites distinctly different from those phosphorylated by cAMP-dependent and Ca+2/phospholipid-dependent MAP kinases. Quantitative analysis further indicated that approximately 19% of the total endogenous kinase activity in brain microtubules was due to FA. Taken together, the results provide initial evidence that the ATP.Mg-dependent protein phosphatase activating factor (FA) is a potent and unique MAP kinase, and may represent one of the major factors involved in phosphorylation of brain microtubules.
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PMID:Identification and characterization of the ATP.Mg-dependent protein phosphatase activator (FA) as a microtubule protein kinase in the brain. 165 23

HMG 14 and protamine can be used to enhance intermolecular ligation of low concentrations of linear DNA. Adding HMG 14 (50 moles per mole DNA) caused 50% of blunt-ended DNA to form predominantly dimers, and all cohesive-ended DNA to form multimers (greater than 6-mer) in response to T4 ligase. Protamine was maximally effective at 40:1, producing mostly dimers and trimers. Adding higher concentrations of HMG 14 did not affect the ligation pattern of cohesive-ended DNA, while higher concentrations of protamine inhibit the formation of multimers. Phosphorylation of HMG 14 at Ser 20 by Ca(++)-phospholipid dependent protein kinase abolished the ability of HMG 14 to stimulate intermolecular ligation, but did not substantially interfere with intramolecular ligation, or the binding of HMG 14 to linear or circular DNA as assessed by gel mobility. Thus Ser 20, which is located in the amino terminal DNA-binding domain of HMG 14, appears to modulate DNA-DNA interactions.
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PMID:HMG 14 and protamine enhance ligation of linear DNA to form linear multimers: phosphorylation of HMG 14 at Ser 20 specifically inhibits intermolecular DNA ligation. 184 50

Incubation of tryptophanyl-tRNA synthetase from bovine pancrease with [gamma-32P]ATP of [gamma-32P]GTP and casein kinase II from rabbit liver leads to the incorporation of labeled phosphate into serine residues of synthetase polypeptide. The maximal level of 32P incorporation into synthetase polypeptide (Mr = 60 kDa) 0.15 moles of 32P per 1 mole of polypeptide was observed. Electrophoretic analysis according to O'Farrell showed that kinase phosphorylates exclusively the most acidic polypeptides (pI 4.9) of the synthetase preparation. Pretreatment of synthetase with animal acidic and alkaline phosphatases had no influence on the level of 32P incorporation in synthetase during subsequent incubation in the presence of casein kinase II.
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PMID:[Phosphorylation of tryptophanyl-tRNA-synthetase by casein kinase type II]. 209 10

Casein kinase II from bovine brain transfers about one mole of phosphate to a serine residue near the COOH terminus of the heavy chain of myosin isolated from bovine brain. We have purified and characterized a peptide that contains this phosphoserine. The peptide was generated by chymotryptic and thermolytic digestion and was isolated by gel filtration, Fe3+ affinity chromatography, and reverse-phase high pressure liquid chromatography. Its sequence, Leu-Glu-Leu-Ser(PO4)-Asp-Asp-Asp-Asp-Glu-Ser-Lys-Ala-Ser-(Xaa)-Ile-Asn-Glu-Thr- Gln-Pro-Pro-Gln, shows that the Ser(PO4) is in an acidic environment, as is typical for casein kinase II phosphorylation sites. The "hydrophobic repeat" typical of alpha-helical coiled-coils is absent, suggesting that the sequence is part of a non-helical "tail piece" of the heavy chain. A synthetic peptide corresponding to residues 1-9 is shown to be an effective substrate for casein kinase II.
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PMID:Amino acid sequence around the serine phosphorylated by casein kinase II in brain myosin heavy chain. 210 26

Cyclic AMP-dependent phosphorylation of the rat brain sodium channel was reported to be restricted to five sites within an approximately 210 amino acid region of the primary sequence that is deleted in the homologous sodium channel from rat skeletal muscle. We find that, in spite of this deletion, the rat muscle sodium channel alpha-subunit is also an excellent substrate for phosphorylation by this kinase both in primary muscle cells in tissue culture and in vitro after isolation from adult muscle. Sodium channel protein purified from adult rat skeletal muscle was readily phosphorylated in vitro by the catalytic subunit of the bovine cyclic AMP-dependent protein kinase (PKa). Only the 260,000 MW alpha-subunit was labeled, with a maximum level of incorporation in vitro of approximately 0.5 mol [32P]phosphate per mole of channel protein. The beta-subunit of the channel is not phosphorylated under these conditions. In primary rat skeletal muscle cells in culture, incorporation of phosphate into the channel alpha-subunit is stimulated 1.3- to 1.5-fold by treatment of the cells with forskolin. Phosphorylation of the sodium channel isolated from these cells could also be demonstrated in vitro using PKa. This in vitro phosphorylation could be inhibited 80-90% by pretreatment of the cells in culture with forskolin, suggesting that the sites labeled in vitro by PKa were the same as those phosphorylated in the intact cells by the endogenous cyclic AMP-dependent kinase. In both the adult muscle channel and the channel from muscle cells in culture, phosphorylation by PKa was limited to serine residues.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphorylation of the rat skeletal muscle sodium channel by cyclic AMP-dependent protein kinase. 215 54

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


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