Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The amino-terminal amino acid sequences of gp85 and gp37, the envelope glycoproteins of Rous sarcoma virus (RSV), were determined. Alignment of these sequences with the amino acid sequence predicted from the complete nucleotide sequence of the Prague strain of RSV, subgroup C (PR-C), has allowed us to delineate the env gene-coding region of this virus. The coding sequences for gp85 and gp37 have been placed in an open reading frame that extends from nucleotide 5045 to nucleotide 6862 and predict sizes of 341 amino acids (36,962 molecular weight) for gp85 and 198 amino acids (21,566 molecular weight) for gp37. Carbohydrate makes a significant contribution to the observed molecular weights of these polypeptides--the amino acid sequence contains 14 potential glycosylation sites (Asn-X-Ser/Thr) in gp85 and two in gp37. Experiments aimed at estimating the number of carbohydrate side chains yielded results consistent with most or all of these sites being occupied. Although an initiation codon is located early (codon 4) in the open reading frame, it is likely that splicing yields an mRNA on which translation initiates at the same AUG as that of the gag gene to produce a nascent polypeptide in which gp85 is preceded by a 62-amino-acid-long leader peptide. This leader contains the hydrophobic sequence (signal sequence) necessary for translocation across the endoplasmic reticulum and is completely removed from the env gene product during translation. The polyprotein precursor, Pr95env, is cleaved to gp85 and gp37 at the carboxyl side of the basic sequence:-Arg-Arg-Lys-Arg-. gp85 is attached through a disulphide linkage to gp37, and although the positions of the cysteines involved in this linkage are not known, the presence of a 27-amino-acid-long hydrophobic region at the carboxy-terminus of gp37 is consistent with its role as a membrane anchor for the viral glycoprotein complex. The location of host range variable regions with respect to the possible tertiary structure of the complex is discussed.
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PMID:Complete sequence of the Rous sarcoma virus env gene: identification of structural and functional regions of its product. 630 51

The ability of polyoma virus to transform cells results primarily from the action of one of the virus-coded early proteins, called middle-T antigen. Middle-T has an associated tyrosine-specific protein kinase activity that can be measured in vitro and results in the phosphorylation of middle-T itself. Almost all mutants so far tested that lack the ability to transform cells, also lack associated kinase activity. Attempts to map within middle-T the tyrosine residue(s) that are phosphorylated in vitro suggest that a likely site of phosphorylation is tyrosine 315 (refs 8-10 and unpublished results). The amino acid sequence preceding Tyr 315 includes a tract of six contiguous glutamic acid residues and bears some homology with that preceding the tyrosine phosphorylated in vivo in pp60v-src, the transforming protein of Rous sarcoma virus, and with a region in the polypeptide hormone, gastrin, preceding a tyrosine that is sulphated. Furthermore, although surprisingly large tracts of middle-T may be removed without affecting its transforming activity, mutants that lack the sequences corresponding to amino acids 311-318 inclusive are transformation defective. Because the likely site of phosphorylation, the homology with pp60v-src and gastrin and the sequence apparently required for transformation all overlap, it has generally been accepted that this region of middle-T may form part of an essential region, possibly an active site on the protein. Here we have used techniques of site-directed and site-specific mutagenesis to probe the sequence requirements in more detail. Contrary to expectation, the results obtained strongly suggest that Tyr 315 and conservation of the surrounding amino acid sequence are not essential for transformation.
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PMID:Transforming activity of polyoma virus middle-T antigen probed by site-directed mutagenesis. 630 61

We investigated the interaction of the avian retrovirus pp12 protein with viral RNA to assess its possible role in virion assembly. Using chemical modification techniques, we found that reagents specific for lysine or arginine residues inactivated the RNA-binding capacity of the protein. The binding of pp12 to 60S viral RNA was also strongly affected by pH (pKapp of 5.5); the affinity for viral RNA decreased by as much as 40-fold after protonation of one or more titratable groups on the protein. When the protein was cleaved by cyanogen bromide, each of the two polypeptide products bound to RNA (with low affinity), but pH dependence was lost. Thus, an intact protein was required for this effect. Since histidine and phosphoserine residues have pKa values close to the pKapp of the pp12-RNA interaction, they were studied to determine whether they were involved in this process. Each of the two histidyl residues in pp12 had pKa values of 6.2, as determined by proton nuclear magnetic resonance titrations, values too high to account for the pKapp of binding. The involvement of phosphoserine residues, which have pKa values similar to the pKapp, was investigated by removal of phosphate from pp12. When phosphate groups were chemically or enzymatically removed from the avian myeloblastosis virus, Rous sarcoma virus (Pr-C), and PR-E 95C virus pp12 proteins, the Kapp for binding 60S viral RNA was reduced 100-fold at pH 7.5. Thus, it seems possible that phosphorylation of the pp12 protein could favor viral nucleocapsid formation by increasing its affinity for the viral RNA genome. Dephosphorylation could provide for its release from the viral RNA during reverse transcription after viral infection of cells.
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PMID:Characteristics and regulation of interaction of avian retrovirus pp12 protein with viral RNA. 631 93

Talin is a recently identified cytoskeletal protein with a polypeptide molecular weight of 215,000 daltons. In cultured fibroblasts talin has been localized by immunofluorescence in adhesion plaques (focal contacts), in the ruffling membranes and leading lamellae of the cell periphery, and in fibrillar patterns that align with microfilament bundles and/or with cell surface fibronectin. These cellular locations suggest that the protein could function either in the attachment of microfilaments to the plasma membrane or in the organization of microfilaments close to membrane attachment sites. Cell transformation by viruses such as Rous sarcoma virus disrupts the normal organization of talin, and in most transformed cells talin appears distributed diffusely through the cytoplasm. In a few cells talin is detected in doughnut-shaped aggregates, as a ring surrounding a central core of actin. The significance of these structures is uncertain, but in some cells the individual structures will condense to form much larger aggregates with a striking appearance when viewed by immunofluorescence microscopy.
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PMID:Talin: a cytoskeletal component concentrated in adhesion plaques and other sites of actin-membrane interaction. 631 1

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate is mitogenic for normal chicken embryo fibroblasts and also causes these cells to express transiently many properties of cells transformed by Rous sarcoma virus. Since some mitogenic hormones stimulate a tyrosine-specific protein kinase activity, and since the transforming protein of RSV is a tyrosine-specific protein kinase, we have examined whether TPA also stimulates protein phosphorylation on tyrosine. We report here that TPA treatment of normal cells resulted in a very rapid phosphorylation on tyrosine of a protein peak of Mr 40 to 43 kilodaltons. Thus, a similar biochemical activity (tyrosine phosphorylation) is associated with the action of polypeptide mitogenic hormones, Rous sarcoma virus and a tumor promoter. In addition, TPA treatment resulted in rapid changes in phosphorylation of proteins on serine and threonine.
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PMID:A tumor promoter stimulates phosphorylation on tyrosine. 641 72

We report the isolation of a specific protease zymogen from chicken plasma. The purification procedure involves barium citrate precipitation, ammonium sulfate fractionation, removal of plasminogen and plasmin on lysine-Sepharose, followed by anion and cation exchange, and gel permeation chromatography. Based on quantitative radioimmunoassay the zymogen is present in plasma at a concentration of 160 mg/liter, and it is obtained by our procedure in highly purified form with a yield of 1.4%. The single polypeptide chain contains an NH2-terminal alanine residue. The native molecule migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 84,000 under reducing conditions. It can be identified as an inactive proenzyme because it has very low amidolytic activity, does not react with the fluorescent active site titrant 4-methyl-lumbelliferyl p-guanidinobenzoate, and does not incorporate radioactive [3H]diisopropylfluorophosphate. It is very susceptible to limited proteolysis which converts it to an active enzyme with trypsin-like specificity. The active enzyme, likewise a single polypeptide chain, migrates as a doublet with apparent molecular weights of 39,000 and 40,000. Its amidolytic activity with synthetic peptide substrates is at least 40-fold higher than that of the proenzyme, it reacts efficiently with 4-methylumbelliferyl p-guanidinobenzoate, and incorporates [3H]diisopropylfluorophosphate while undergoing irreversible inactivation. The enzyme appears to be a reasonably efficient plasminogen activator in zymographic gels, but not in solution. With human high molecular weight kininogen as substrate the enzyme was about 25% as efficient as human plasma kallikrein. It lacks any plasminogen-independent proteolytic activity with other protein substrates, and it hydrolyzes small peptide substrates designed for both human kallikrein and urinary urokinase, respectively. Inhibition studies with peptide chloromethyl ketones indicate enzymatic properties closer to human plasma kallikrein than to the human plasminogen activator urokinase (EC 3.4.21.31). The chicken plasma enzyme and the plasminogen activator from the conditioned media of Rous sarcoma virus-transformed chick embryo fibroblasts treated with tumor promoter are different by criteria of tryptic peptide maps, and amino acid composition and enzymatic specificity. The designations chicken plasma prekallikrein plasminogen proactivator and chicken plasma kallikrein plasminogen activator are proposed for the zymogen and enzyme forms, respectively. Using rabbit antibodies against the proenzyme we developed a solid phase immunoadsorption procedure that allowed us to isolate the protein with an overall yield of 11.4%.
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PMID:A proenzyme from chicken plasma similar to human plasma prekallikrein. 655 13

Previous studies have established that glucose deprivation of murine cells suppresses the synthesis of an Mr = 85,000 polypeptide. A protein of approximately the same molecular weight has been found to be associated with the transforming protein of Rous sarcoma virus, pp60src. The present study compares the Mr = 85,000 glucose-regulated protein with the pp60src-associated protein. By the criteria of mobility in sodium dodecyl sulfate-polyacrylamide gels and one-dimensional partial proteolytic peptide mapping the two proteins appear to be identical. It has previously been shown that the pp60src-associated protein is also identical with one of several proteins whose synthesis is induced after growth of cells at elevated temperatures or in the presence of arsenite and canavanine. Considering that it is involved in a number of complex response patterns, the name syndromin is proposed for this protein. These findings open the possibility of a fundamental interrelationship among the heat shock effect, regulation of protein synthesis by glucose deprivation, and oncogenic transformation by Rous sarcoma virus.
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PMID:A major cytoplasmic glucose-regulated protein is associated with the Rous sarcoma virus pp60src protein. 680 76

An Mr 21 000 polypeptide, designated APPG, has been purified by reverse-phase, high-performance liquid chromatography (RP-HPLC), from acid extracts of porcine anterior pituitary glands. This acidic protein possesses an isoelectric point of 4.9. Amino acid analysis shows that it is not a glycoprotein and estimates it to contain about 173 amino acids. NH2-terminal sequence analysis allowed the determination of the first 50 residues unambiguously. A computer data bank search using a mutation data matrix and comparison with 269 012 protein segments indicated that this is a novel polypeptide sequence. However, this search revealed suggestive sequence homologies to a number of peptides of known sequence, including duck proinsulin (30%), Rous sarcoma virus transforming protein TVFV60 (24%) and pig secretin (26%).
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PMID:Isolation and NH2-terminal sequence of a novel porcine anterior pituitary polypeptide. Homology to proinsulin, secretin and Rous sarcoma virus transforming protein TVFV60. 681 30

The stable expression of the alpha chain of the feline cytotoxic T cell differentiation antigen (fCD8 alpha) on Crandell feline kidney cells (CRFK) was carried out by using an expression vector which contains the Rous sarcoma virus long terminal repeat and a neo resistant gene. After three rounds of cloning under G418 selection for over two months, the expression of the feline polypeptide was detected by human monoclonal antibody OKT8.
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PMID:Stable expression of the cDNA encoding the feline CD8 alpha gene. 786 71

The NS-1 gene of the parvovirus minute virus of mice (MVM) (prototype strain, MVMp) was fused in phase with the sequence coding for the DNA-binding domain of the bacterial LexA repressor. The resulting chimeric protein, LexNS-1, was tested for its transcriptional activity by using various target promoters in which multiple LexA operator sequences had been introduced. Under these conditions, NS-1 was shown to stimulate gene expression driven by the modified long terminal repeat promoters (from the retroviruses mouse mammary tumor virus and Rous sarcoma virus) and P38 promoter (from MVMp), indicating that the NS-1 protein is a potent transcriptional activator. It is noteworthy that in the absence of LexA operator-mediated targeting, the genuine mouse mammary tumor virus and Rous sarcoma virus promoters were inhibited by NS-1. Together these data strongly suggest that NS-1 contains an activating region able to induce promoters with which this protein interacts but also to repress transcription from nonrecognized promoters by a squelching mechanism similar to that described for other activators. Deletion mutant analysis led to the identification of an NS-1 domain that exhibited an activating potential comparable to that of the whole polypeptide when fused to the DNA-binding region of LexA. This domain is localized in the carboxy-terminal part of NS-1 and corresponds to one of the two regions previously found to be responsible for toxicity. These results argue for the involvement of the regulatory functions of NS-1 in the cytopathic effect of this parvovirus product.
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PMID:Targeting of promoters for trans activation by a carboxy-terminal domain of the NS-1 protein of the parvovirus minute virus of mice. 796 88


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