Related Experiment Videos
Molecular dynamics simulations of the Ras:Raf and Rap:Raf complexes
J Zeng1, H R Treutlein, T Simonson
1Laboratoire de Biologie Structurale (CNRS), IGBMC Illkirch (C.U. de Strasbourg), France.
Abstract:
The protein Raf is an immediate downstream target of Ras in the MAP kinase signalling pathway. The complex of Ras with the Ras-binding domain (RBD) of Raf has been modelled by homology to the (E30D,K31E)-Rap1A:RBD complex, and both have been subjected to multiple molecular dynamics simulations in solution. While both complexes are stable, several rearrangements occur in the Ras:RBD simulations: the RBD loop 100-109 moves closer to Ras, Arg73 in the RBD moves towards Ras to form a salt bridge with Ras-Asp33, and Loop 4 of the Ras switch II region shifts upwards toward the RBD. The Ras:RBD interactions (including the RBD-Arg73 interaction) are consistent with available NMR and mutagenesis data on the Ras: RBD complex in solution. The Ras switch II region does not interact directly with the RBD, although indirect interactions exist through the effector domain and bridging water molecules. No large-scale RBD motion is seen in the Ras:RBD complex, compared to the Rap:RBD complex, to suggest an allosteric activation of Raf by Ras. This may be because the Raf kinase domain (whose structure is unknown) is not included in the model.
Insights
Ras protein interactions with Raf's Ras-binding domain (RBD) were simulated. Molecular dynamics revealed stable complexes with specific rearrangements, but no large-scale motion suggesting allosteric activation of Raf by Ras.
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- Ras proteins are key regulators in cellular signaling pathways, including the MAP kinase pathway.
- Raf is an immediate downstream target of Ras, and its activation is crucial for downstream signaling.
- Understanding the molecular interactions between Ras and Raf's Ras-binding domain (RBD) is essential for deciphering signal transduction mechanisms.
Purpose of the Study:
- To model and simulate the complex of Ras with the Ras-binding domain (RBD) of Raf.
- To investigate the dynamic interactions and stability of the Ras:RBD complex in solution.
- To explore potential mechanisms of allosteric activation of Raf by Ras based on structural dynamics.
Main Methods:
- Homology modeling was used to create the Ras:RBD complex structure, based on the Rap1A:RBD complex.
- Multiple molecular dynamics simulations were performed on the modeled Ras:RBD complex in solution.
- Analysis of simulation trajectories focused on conformational changes, inter-residue interactions, and domain motions.
Main Results:
- The Ras:RBD complex was found to be stable, with notable rearrangements including RBD loop movements and salt bridge formation between Arg73 (RBD) and Asp33 (Ras).
- Ras switch II region interactions with RBD were indirect, mediated by the effector domain and water molecules, not direct contact.
- No significant large-scale motion of the RBD was observed in the Ras:RBD complex compared to Rap:RBD, questioning direct allosteric activation.
Conclusions:
- The simulated Ras:RBD interactions align with existing experimental data from NMR and mutagenesis studies.
- The lack of observed large-scale RBD motion suggests that allosteric activation of Raf by Ras might not occur through simple domain dynamics alone.
- The absence of the Raf kinase domain in the model may limit the interpretation of allosteric activation mechanisms.