At high concentrations, free radicals and radical-derived, nonradical reactive species are hazardous for living organisms and damage all major cellular constituents. At moderate concentrations, how...

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Free Radicals in the Physiological Control of Cell Function

Cell signaling by receptor-tyrosine kinases

The adhesive interactions of cells with other cells and with the extracellular matrix are crucial to all developmental processes, but have a central role in the functions of the immune system throughout life Three families of cell-surface molecules regulate the migration of lymphocytes and the interactions of activated cells during immune responses

Adhesion receptors of the immune system.

Roles moleculaires des proteines de choc thermique dans le fonctionnement des organismes a des temperatures normales et suite a des chocs thermiques; differents genes impliques

The heat-shock proteins

https://www.cell.com/cell/pdf/S0092-8674(00)80209-3.pdf

Osteoprotegerin: A Novel Secreted Protein Involved in the Regulation of Bone Density

The protein kinase activity associated with pp60src, the transforming protein of Rous sarcoma virus, was found to phosphorylate tyrosine when assayed in an immunoprecipitate. Despite the fact that a protein kinase with this activity has not been described before, several observations suggest that pp60src also phosphorylates tyrosine in vivo. First, chicken cells transformed by Rous sarcoma virus contain as much as 8-fold more phosphotyrosine than do uninfected cells. Second, phosphotyrosine is present in pp60src itself, at one of the two sites of phosphorylation. Third, phosphotyrosine is present in the 50,000-dalton phosphoprotein that coprecipitates with pp60src extracted from transformed chicken cells. We infer from these observations that pp60src is a novel protein kinase and that the modification of proteins via the phosphorylation of tyrosine is essential to the malignant transformation of cells by Rous sarcoma virus. pp60sarc, the closely related cellular homologue of viral pp60src, is present in all vertebrate cells. This normal cellular protein, obtained from both chicken and human cells, also phosphorylated tyrosine when assayed in an immunoprecipitate. This is additional evidence of the functional similarity of these structurally related proteins and demonstrates that all uninfected vertebrate cells contain at least one protein kinase that phosphorylates tyrosine.

https://www.pnas.org/content/pnas/77/3/1311.full.pdf

Transforming gene product of Rous sarcoma virus phosphorylates tyrosine

Publisher Summary This chapter discusses the detection and quantification of phosphotyrosine in proteins. Protein kinases can be differentiated according to their amino acid specificity. Casein kinases of type II and the cAMP-dependent kinases phosphorylate serine, while casein kinases of type I phosphorylate threonine and, to a lesser extent, serine. Another group of kinases with strict specificity for tyrosine is described in the chapter. Most tyrosine-specific protein kinase activities detected to date are implicated in cell growth control. They include the kinases associated with the cell surface receptors for two polypeptide growth factors, epidermal growth factor (EGF) and platelet-derived growth factor (PDGF), and with the transforming proteins of at least five genetically distinct groups of retroviruses. The activity of a tyrosine protein kinase in the cell is apparent from an increase in the gross level of phosphotyrosine in cell proteins. The induction of a cellular tyrosine protein kinase by growth factors or the introduction of a viral tyrosine protein kinase by infection can raise the proportion of acid-stable protein bound phosphate present as phosphotyrosine 5–10 times. Phosphatases specific for tyrosine are as yet poorly characterized, but may be inhibited by traces of Zn 2+ or by adding free phosphotyrosine or analogs. The simplest strategy is to lyse cells directly into a denaturing solution, or to stop an in vitro reaction with denaturing agents.

Detection and quantification of phosphotyrosine in proteins.

https://www.cell.com/cell/pdf/0092-8674(81)90512-2.pdf

Vinculin: a cytoskeletal target of the transforming protein of Rous sarcoma virus.

Evidence that the phosphorylation of tyrosine is essential for cellular transformation by Rous sarcoma virus

CD45 is a family of high molecular weight leukocyte cell surface glycoproteins. Recently, two related subregions of the cytoplasmic domain of CD45 have been shown to have 30-40% amino acid identity with a human placental protein phosphotyrosine phosphatase, and CD45 isolated from human spleen was found to exhibit intrinsic protein phosphotyrosine phosphatase (EC 3.1.3.48) activity. In the present studies, we demonstrate that each of the known isoforms of murine CD45 has an equivalent basal level of protein phosphotyrosine phosphatase activity and establish that this enzymatic activity is associated with the cytoplasmic domain of the glycoprotein. Studies with three independent sets of well-characterized parental CD45+, mutant CD45-, and revertant CD45+ lymphoma cell lines indicate that loss of CD45 increases the phosphorylation of the src-related leukocyte-specific tyrosine protein kinase p56lck on tyrosine-505, a putative negative regulatory site. This suggests that CD45 may play a role in leukocyte growth regulation by altering the kinase activity of p56lck.

https://www.pnas.org/content/pnas/86/22/8959.full.pdf

Bartholomew M. Sefton

Papers

Transforming gene product of Rous sarcoma virus phosphorylates tyrosine

Detection and quantification of phosphotyrosine in proteins.

Vinculin: a cytoskeletal target of the transforming protein of Rous sarcoma virus.

Evidence that the phosphorylation of tyrosine is essential for cellular transformation by Rous sarcoma virus

Expression of CD45 alters phosphorylation of the lck-encoded tyrosine protein kinase in murine lymphoma T-cell lines.