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A RasGTP-induced conformational change in C-RAF is essential for accurate molecular recognition

Kayo Hibino1, Tatsuo Shibata, Toshio Yanagida

  • 1Cellular Informatics Laboratory, RIKEN, Wako, Japan.

Biophysical Journal
|September 2, 2009
PubMed

Insights

Ras-RAF signaling is crucial in cancer. New research reveals how C-RAF distinguishes active RasGTP from inactive RasGDP by changing its conformation, a key step in molecular recognition.

Area of Science:

  • Molecular biology
  • Cellular signaling
  • Cancer research

Background:

  • Ras-RAF signaling pathway dysregulation is implicated in numerous human cancers.
  • The precise kinetic and dynamic mechanisms of Ras-RAF molecular recognition are not fully understood.

Purpose of the Study:

  • To investigate how C-RAF distinguishes between active RasGTP and inactive RasGDP in living cells.
  • To elucidate the role of C-RAF conformational changes in Ras-RAF molecular recognition.

Main Methods:

  • Development of a technique for imaging single-pair fluorescence resonance energy transfer (spFRET) in living cells.
  • Coupling spFRET with single-molecule kinetic analysis to study Ras-RAF interactions.
  • Utilizing C-RAF mutants lacking conformational flexibility.

Main Results:

  • Full-length C-RAF, but not its fragments, efficiently detected Ras activity switching in living cells.
  • RasGDP binds to closed-conformation C-RAF; RasGTP binding induces C-RAF to adopt an open conformation, enhancing interaction.
  • Spontaneous C-RAF conformational changes from closed to open states are rare in quiescent cells.
  • C-RAF mutants unable to undergo conformational changes failed to differentiate between RasGDP and RasGTP.

Conclusions:

  • RasGTP actively manipulates the conformation of its effector, C-RAF, which is essential for specific molecular recognition.
  • Conformational change in effector molecules is a newly identified function of RasGTP.
  • Understanding these dynamics offers insights into cancer signaling and potential therapeutic targets.

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