Activation of the pp60c-src kinase by middle T antigen binding or by dephosphorylation.

Research output: Contribution to journalArticle

208 Citations (Scopus)

Abstract

The transforming protein of polyoma virus, middle T antigen, associates with the protein tyrosine kinase pp60c-src, and analysis of mutants of middle T suggests that this complex plays an important role in transformation by polyoma. It has recently been reported that pp60c-src from polyoma virus-transformed cells has enhanced tyrosine kinase activity in vitro. The data presented here confirm these findings and show that the enhanced kinase activity of pp60c-src is due to an increase in the Vmax of the enzyme. Sucrose density gradient analysis demonstrates that only the form of pp60c-src which is bound to middle T antigen is activated. The difference in enzyme activity between pp60c-src from normal and middle T-transformed cells is more marked when the enzyme is prepared from lysates containing the phosphotyrosine protein phosphatase inhibitor, sodium orthovanadate. pp60c-src from middle T transformed cells is unaffected, but pp60c-src from normal cells has reduced kinase activity if dephosphorylation is prevented. The kinase activity of pp60c-src thus appears to be regulated by its degree of phosphorylation at tyrosine, and data are presented which support this hypothesis. pp60c-src is the first example of a protein tyrosine kinase whose activity is inhibited by phosphorylation at tyrosine. Middle T antigen may increase the kinase activity of pp60c-src by preventing phosphorylation at this regulatory site.

Original languageEnglish (US)
Pages (from-to)1471-1477
Number of pages7
JournalEMBO Journal
Volume4
Issue number6
StatePublished - Jun 1985
Externally publishedYes

Fingerprint

src-Family Kinases
Viral Tumor Antigens
Phosphorylation
Phosphotransferases
Chemical activation
Polyomavirus
Viruses
Protein-Tyrosine Kinases
Tyrosine
Enzymes
Phosphotyrosine
Protein Tyrosine Phosphatases
Vanadates
Phosphoprotein Phosphatases
Enzyme activity
Sucrose
Sodium
Proteins

ASJC Scopus subject areas

  • Cell Biology
  • Genetics

Cite this

Activation of the pp60c-src kinase by middle T antigen binding or by dephosphorylation. / Courtneidge, Sara.

In: EMBO Journal, Vol. 4, No. 6, 06.1985, p. 1471-1477.

Research output: Contribution to journalArticle

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