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A protein tyrosine kinase involved in regulation of pp60c-src function

M Okada1, H Nakagawa

  • 1Division of Protein Metabolism, Osaka University, Japan.

The Journal of Biological Chemistry
|December 15, 1989
PubMed

Insights

A novel tyrosine kinase phosphorylates intact pp60c-src at its C-terminus, distinct from autophosphorylation sites. This phosphorylation regulates pp60c-src activity by decreasing its Vmax, supporting its role as a kinase regulator.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Signaling

Background:

  • A novel protein tyrosine kinase was previously identified.
  • This kinase specifically phosphorylates truncated pp60c-src at a distinct tyrosine residue.

Purpose of the Study:

  • To investigate if the novel kinase phosphorylates intact pp60c-src.
  • To determine the specific phosphorylation site on intact pp60c-src.
  • To elucidate the functional consequences of this phosphorylation on pp60c-src activity.

Main Methods:

  • Purification of non-neuronal and neuronal forms of intact pp60c-src from neonatal rat brain.
  • Phosphorylation assays using the novel kinase and intact pp60c-src.
  • Peptide mapping using trypsin and chymotrypsin digestion.
  • Analysis of kinase activity and kinetic experiments.

Main Results:

  • The novel kinase phosphorylates both non-neuronal and neuronal forms of intact pp60c-src on tyrosine residues.
  • The phosphorylation site was identified as a C-terminal tyrosine residue, homologous to chicken Tyr527.
  • Phosphorylation by the novel kinase decreased pp60c-src activity by reducing its Vmax.
  • The enzyme also phosphorylated pp60c-src with destroyed kinase activity.

Conclusions:

  • The novel tyrosine kinase phosphorylates intact pp60c-src at the C-terminal Tyr527 residue.
  • This phosphorylation event negatively regulates pp60c-src enzymatic activity.
  • The findings support the role of the novel tyrosine kinase as a specific regulator of pp60c-src in cellular processes.

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