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)

Phosphorylation of a phosphotyrosine-containing 120,000 Da protein (pp120) in Rous sarcoma virus (RSV)-infected mammalian cells and in in vitro protein kinase reactions was examined. Phosphorylated pp120 was co-immunoprecipitated with anti-pp60v-src antibodies only from RSV-transformed or revertant vole fibroblasts which contained active pp60v-src tyrosine kinase activity or from temperature-sensitive RSV-infected vole cells grown at the permissive temperature. Pp120 was phosphorylated on tyrosine in in vitro immune complex kinase reactions containing both pp120 and enzymatically active pp60v-src. Inhibition of pp60v-src's kinase activity blocked phosphorylation of pp120 in vitro. These results support the proposal that pp120 tyrosine phosphorylation is pp60v-src-dependent and that pp120 may thus serve as a substrate of pp60v-src in RSV-transformed mammalian cells.
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PMID:Evidence that a phosphotyrosine-containing 120,000 Da protein from Rous sarcoma virus-infected cells is phosphorylated by pp60v-src. 247 91

Pig heart tissue have been shown to contain 3 different 60,000 Da phosphoproteins. Different purification procedures were used in order to separate them, suggesting that the 3 phosphoproteins differ in their environmental parameters. The 2 major ones appear essentially as peripheral phosphoproteins that are associated with cellular membranes through ionic forces, whereas the third minor phosphoprotein behaves as an integral plasma membrane protein. The three phosphoproteins also differ in their relative amount of phosphorylated serine, threonine and tyrosine residues after in vitro protein kinase assay. Evidence that the 3 phosphoproteins are related arises from the similarity between their respective phosphopeptide maps after partial hydrolysis with proteases, an experiment that also points out relatedness in primary structure between them and the transforming protein of Rous sarcoma virus, pp60v-src. The 3 phosphoproteins, however, do not appear to be immunologically related to pp60v-src since none of them is immunoprecipitated by sera that precipitate pp60v-src. The possibility that the three 60,000 Da phosphoproteins under study represent 3 differentially localized and phosphorylated products of c-src and/or c-src related genes is discussed.
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PMID:Studies in pig heart tissue on various 60,000 Da phosphoproteins. 247 41

The c-src protein isolated from neuronal cells (pp60c-src+) displays a higher level of protein kinase activity than does pp60c-src from nonneural tissues. There are two structural alterations present in the amino-terminal half of pp60c-src+ expressed in neurons which could contribute to the enhanced activity of this form of pp60c-src: (i) a hexapeptide insert located at amino acid 114 of avian pp60c-src+ and (ii) a novel site(s) of serine phosphorylation. We characterized pp60c-src+ expressed in a nonneuronal cell type to identify factors that regulate the activity of the c-src+ protein and the importance of the neuronal environment on this regulation. The c-src+ protein overexpressed in chicken embryo fibroblasts (CEFs) displayed higher kinase activity than did pp60c-src. The major sites of phosphorylation of the c-src+ protein were Ser-17 and Tyr-527. The unique site(s) of serine phosphorylation originally identified in pp60c-src+ expressed in neurons was not detected in the c-src+ protein overexpressed in CEFs. Therefore, the hexapeptide insert is sufficient to cause an elevation in the tyrosine protein kinase activity of pp60c-src+. Our data also indicate that CEFs infected with the Rous sarcoma virus (RSV)c-src+ display phenotypic changes that distinguish them from cultures producing pp60c-src and that pp60c-src+-expressing cells are better able to grow in an anchorage-independent manner. The level of total cellular tyrosine phosphorylation in RSVc-src+-infected cultures was moderately higher than the level observed in cultures infected with RSVc-src. This level was not as pronounced as that observed in cells infected with RSVv-src or oncogenic variants of RSVc-src. Thus, pp60c-src+ could be considered a partially activated c-src variant protein much like other c-src proteins that contain mutations in the amino-terminal domain.
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PMID:Biological and biochemical properties of the c-src+ gene product overexpressed in chicken embryo fibroblasts. 247 84

We have constructed seven deletions in the src homology 2 (SH2) domain of the Rous sarcoma virus src gene and have expressed them and wild-type v-src (wt v-src) in Rat 1 fibroblasts. Transfected cells containing mutant DNAs have reduced focus forming activity when compared to cells containing the wt v-src DNA. In most cases, established cell lines that express these mutants have altered growth properties in soft agar. The src proteins isolated from mutant cell lines have reduced tyrosine kinase activity. We also see differences in the phosphorylation of cellular proteins in vivo. Unlike the wt protein kinase, the SH2 domain mutant kinases do not phosphorylate a set of cellular proteins ranging in size from 120-150 kDa.
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PMID:Src homology 2 domain deletion mutants of p60v-src do not phosphorylate cellular proteins of 120-150 kDa. 249 31

Subcellular localization of potential substrates of a tyrosine-protein kinase, p60v-src, was analyzed by cell fractionation in combination with immunoblotting with antiphosphotyrosine antibody. In cells transformed by wild type Rous sarcoma virus, most phosphotyrosine-containing proteins were found both in plasma membranes and in a cytoplasmic matrix structure associated with plasma membranes and resistant to nonionic detergent extraction (plasma membrane matrix). A similar localization of phosphotyrosine-containing proteins was obtained in cells transformed by PRCII, Y73, or Fujinami sarcoma virus. On the other hand, in cells infected with Rous sarcoma virus mutants that encode nonmyristylated p60v-src, tyrosine phosphorylation was found mostly in proteins which were different from those identified in wild type-infected cells and were distributed to both plasma membrane and cytosolic fractions. These results suggest that most cellular substrate proteins, phosphorylation of some of which may be critical for the initiation of transformation, are present primarily in the plasma membrane-matrix structure.
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PMID:Localization of major potential substrates of p60v-src kinase in the plasma membrane matrix fraction. 249 23

We previously showed (V. W. Raymond and J. T. Parsons, Virology 160:400-410, 1987) that variants of the Prague A strain of Rous sarcoma virus containing large deletions impinging on a region of the src gene encoding amino acid residues 143 to 169 were defective for transformation of chicken cells in culture. Here we report that introduction of small (tri-and tetrapeptide) deletions into a region of pp60v-src containing amino acid residues 155 to 175 was found to inactivate transformation. In addition, insertion of four, but not one, amino acid residues at position 161 also inhibited transformation. Biochemical analysis of the src proteins encoded by individual transformation-defective variants revealed that the structural alterations introduced into this domain had only marginal effects upon src tyrosine-specific protein kinase activity. However, the src proteins encoded by defective variants exhibited a significantly shorter half-life within the cell, although these proteins efficiently and rapidly associated with cellular membranes. Our results suggest that the structural domain encompassing residues 155 to 177 may influence the stability of pp60src in the cellular membrane, possibly via the interaction of src with a cellular membrane component(s) or substrate(s).
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PMID:Deletions and insertions within an amino-terminal domain of pp60v-src inactivate transformation and modulate membrane stability. 253 35

The matrix protein from avian myeloblastosis virus and the Rous sarcoma virus, Prague C strain, is a phosphoprotein. A comparison of the amino acid sequences shows these phosphoproteins are very similar. The sites of phosphorylation of the matrix protein purified from virions are identified as serine residues 68 and 106. Treatment with purified rabbit skeletal-muscle protein phosphatase 1 or 2A, selectively releases phosphate from serine 68, while alkali treatment releases phosphate from both sites. When analyzed as a substrate for six different protein kinases, only the Ca2+/phospholipid-dependent protein kinase modifies the matrix protein. The serine residues phosphorylated in vivo are identical to those phosphorylated in vitro by this protein kinase. The role of these phosphorylation events in viral production is discussed.
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PMID:Phosphorylation of avian retrovirus matrix protein by Ca2+/phospholipid-dependent protein kinase. 253 9

A cDNA clone, named T64, was isolated from a library of quail neuroretinal cells transformed by a thermosensitive v-src mutant of Rous sarcoma virus. it corresponds to the most abundant mRNA with thermodependent expression in these cells. T64 accumulation also correlated with pp60v-src activity in other cell types transformed by RSV, such as fibroblasts and myoblasts, but was independent of the proliferative state of the cells, indicating that T64 is rather implicated in the process of morphological transformation. Nuclear run on experiments showed that the accumulation of T64 mRNA in transformed neuroretinal cells is the consequence of an increased transcription rate. Enhancement of T64 expression on QNR cells was also achieved by infection with avian retroviruses harboring other oncogenes with protein kinase activity such as v-fps and v-mil. The 1.6 kb T64 mRNA was detected in vivo in a few quail tissues at levels 50-200-fold lower than in RSV-infected cells. DNA sequencing of the T64 cDNA revealed an open reading frame encoding a 449 amino acids protein with a typical N-terminal signal peptide and with significant amino acid sequence homology with a rat-secreted protein.
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PMID:Expression of a novel gene encoding a 51.5 kD precursor protein is induced by different retroviral oncogenes in quail neuroretinal cells. 254 93

cAMP-dependent protein kinase (PKA; ATP: protein phosphotransferase; EC 2.7.1.37) appears to be the major mediator of cAMP responses in mammalian cells. We have investigated the role of PKA subunits in the regulation of specific genes in response to cAMP by cotransfection of wild-type or mutant subunits of PKA together with cAMP-inducible reporter genes. Overexpression of catalytic subunit induced expression from three cAMP-regulated promoters (alpha-subunit, c-fos, E1A) in the absence of elevated levels of cAMP but did not affect expression from two unregulated promoters (Rous sarcoma virus, simian virus 40). Cotransfection of a regulatory subunit gene containing mutations in both cAMP binding sites strongly repressed both basal and induced expression from the cAMP-responsive alpha-subunit promoter without affecting expression from the Rous sarcoma virus promoter. These experiments indicate that cAMP induces gene expression through phosphorylation by the catalytic subunit and that the ambient degree of phosphorylation dictates the level of basal as well as induced expression of the cAMP-regulated alpha-subunit gene.
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PMID:Regulation of transcription by cyclic AMP-dependent protein kinase. 254 78

Protein myristoylation was first discovered in the catalytic subunit of adenosine 3',5'-cyclic monophosphate-dependent protein kinase. Subsequently, various cellular and viral myristoylated proteins were detected. In each case, the myristoyl moiety was found in an amide linkage with the amino terminal glycine residue of the modified proteins. The biological functions of protein myristoylation of various cellular protein, oncogene product, and viral structural proteins have been studied by many biochemists. Two of the most thoroughly studies myristoylated proteins are the transforming protein of Rous sarcoma virus, pp60v-src, and the proto-oncogene product, pp60c-src. Deletion, modification of the first 14 NH2-terminal amino acid of pp60v-src, or chemical antimyristoylation of the protein with N-myristoyl glycinal diethylacetal does not affect intrinsic tyrosine src-kinase activity, but prevents myristoylation and membrane association, and abolishes the transforming activity of the protein. Protein myristoylations of some viral structural proteins were also studied by many investigators, and X-ray crystallographic studies of poliovirus suggest that myristate moiety may play a central role in capsid assembly. Recently, human immunodeficiency virus, HIV-I, process a myristoylated p17gag protein, which is proteolytically derived from the NH2-terminus of a gag precursor protein, and its myristate moiety may be important for virus assembly. In this review, we detailed recent studies of the protein myristoylation in cellular regulation and virus proliferation.
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PMID:[Function of protein myristoylation in cellular regulation and viral proliferation]. 254 55


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