Transforming Gene Product of Rous Sarcoma Virus Phosphorylates Tyrosine

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 pp...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1980-03, Vol.77 (3), p.1311-1315
Main Authors: Hunter, Tony, Sefton, Bartholomew M.
Format: Article
Language:English
Subjects:
Acid hydrolysis
Amino acids
Avian Sarcoma Viruses - enzymology
Avian Sarcoma Viruses - genetics
Cell Transformation, Viral
Cells, Cultured
Chickens
Electrophoresis
Genes, Viral
Molecular Weight
Phosphates
Phosphoamino acids
Phosphoproteins
Phosphorylation
Protein Kinases - metabolism
src genes
Substrate Specificity
Tyrosine - metabolism
Viral Proteins - metabolism
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Summary: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 pp60srcalso 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 pp60srcitself, at one of the two sites of phosphorylation. Third, phosphotyrosine is present in the 50,000-dalton phosphoprotein that coprecipitates with pp60srcextracted from transformed chicken cells. We infer from these observations that pp60srcis 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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.77.3.1311