cdc25 is a specific tyrosine phosphatase that directly activates p34cdc2

Cell. 1991 Oct 4;67(1):197-211. doi: 10.1016/0092-8674(91)90583-k.


cdc25 controls the activity of the cyclin-p34cdc2 complex by regulating the state of tyrosine phosphorylation of p34cdc2. Drosophila cdc25 protein from two different expression systems activates inactive cyclin-p34cdc2 and induces M phase in Xenopus oocytes and egg extracts. We find that the cdc25 sequence shows weak but significant homology to a phylogenetically diverse group of protein tyrosine phosphatases. cdc25 itself is a very specific protein tyrosine phosphatase. Bacterially expressed cdc25 directly dephosphorylates bacterially expressed p34cdc2 on Tyr-15 in a minimal system devoid of eukaryotic cell components, but does not dephosphorylate other tyrosine-phosphorylated proteins at appreciable rates. In addition, mutations in the putative catalytic site abolish the in vivo activity of cdc25 and its phosphatase activity in vitro. Therefore, cdc25 is a specific protein phosphatase that dephosphorylates tyrosine and possibly threonine residues on p34cdc2 and regulates MPF activation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • CDC2 Protein Kinase / genetics*
  • CDC2 Protein Kinase / metabolism
  • Cell Cycle Proteins*
  • Cloning, Molecular
  • Drosophila / enzymology*
  • Enzyme Activation
  • Female
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Oligodeoxyribonucleotides
  • Oocytes / physiology
  • Peptide Fragments / isolation & purification
  • Protein Tyrosine Phosphatases / genetics*
  • Protein Tyrosine Phosphatases / metabolism
  • RNA, Messenger / genetics
  • Sequence Homology, Nucleic Acid
  • Substrate Specificity
  • Transcription, Genetic
  • Xenopus
  • ras-GRF1*


  • Cell Cycle Proteins
  • Fungal Proteins
  • Oligodeoxyribonucleotides
  • Peptide Fragments
  • RNA, Messenger
  • ras-GRF1
  • CDC2 Protein Kinase
  • Protein Tyrosine Phosphatases