Csk inhibition of c-Src activity requires both the SH2 and SH3 domains of Src

EMBO J. 1993 Jul;12(7):2625-34.


The protein tyrosine kinase c-Src is negatively regulated by phosphorylation of Tyr527 in its carboxy-terminal tail. A kinase that phosphorylates Tyr527, called Csk, has recently been identified. We expressed c-Src in yeast to test the role of the SH2 and SH3 domains of Src in the negative regulation exerted by Tyr527 phosphorylation. Inducible expression of c-Src in Schizosaccharomyces pombe caused cell death. Co-expression of Csk counteracted this effect. Src proteins mutated in either the SH2 or SH3 domain were as lethal as wild type c-Src, but were insensitive to Csk, even though they were substrates for Csk in vivo. Peptide binding experiments revealed that Src proteins with mutant SH3 domains adopted a conformation in which the SH2 domain was not interacting with the tail. These data support the model of an SH2 domain-phosphorylated tail interaction repressing c-Src activity, but expand it to include a role for the SH3 domain. We propose that the SH3 domain contributes to the maintenance of the folded, inactive configuration of the Src molecule by stabilizing the SH2 domain-phosphorylated tail interaction. Moreover, the system we describe here allows for further study of the regulation of tyrosine kinases in a neutral background and in an organism amenable to genetic analysis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • CSK Tyrosine-Protein Kinase
  • Cloning, Molecular
  • Genes, Lethal
  • Molecular Sequence Data
  • Mutation
  • Peptides / metabolism
  • Phenotype
  • Phosphorylation
  • Protein Conformation
  • Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism*
  • Proto-Oncogene Proteins pp60(c-src) / antagonists & inhibitors*
  • Proto-Oncogene Proteins pp60(c-src) / genetics
  • Proto-Oncogene Proteins pp60(c-src) / metabolism
  • Schizosaccharomyces / genetics
  • Substrate Specificity
  • Tyrosine / metabolism
  • src-Family Kinases


  • Peptides
  • Tyrosine
  • Protein-Tyrosine Kinases
  • CSK Tyrosine-Protein Kinase
  • Proto-Oncogene Proteins pp60(c-src)
  • src-Family Kinases