To initiate MAPK signaling, the RBD and CRD domains of Raf bind to active Ras at the plasma membrane. For this Ras/Raf complex, the orientation of Ras relative to the membrane may be critical for signaling. To explore the motions of Raf-CRD and how they may affect the membrane-orientation of Ras, we perform molecular simulations of KRAS4b bound to RBD-CRD of Raf-1, in solution and at a membrane of an 8-lipid mixture. In solution (without the membrane), the simulations capture a heterogeneous Ras/CRD interface, indicating that the CRD can rotate within a Ras:RBD-CRD complex. At the membrane, the calculations show how Ras/Raf-membrane interactions and the mobility of CRD lead to a signaling-capable configuration on the membrane. Specifically, the CRD undergoes a distinct movement that stabilizes Ras in an orientation where its helices α3-5 are exposed from the membrane surface. The simulated membrane-orientations of the Ras:RBD-CRD complex are highly consistent with recent NMR measurements. Our calculations complement these experiments by elucidating a relationship between CRD movement and Ras membrane orientation. Together, these findings help establish the precise role of CRD in Ras/Raf-membrane interaction, and may suggest novel therapeutic strategies for controlling cancers.

Role of membrane in regulating the Ras/Raf signaling complex

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.