Abstract
About a quarter of total human cancers carry mutations in Ras isoforms. Accumulating evidence suggests that small GTPases, RalA and RalB, and their activators, Ral guanine nucleotide exchange factors (RalGEFs), play an essential role in oncogenic Ras-induced signalling. We studied the interaction between human K-Ras4B and the Ras binding domain (RBD) of Rgl2 (Rgl2RBD), one of the RBD-containing RalGEFs. We show that the G12V oncogenic K-Ras4B mutation increases the affinity with Rgl2RBD. The crystal structure of the K-Ras4BG12V: Rgl2RBD complex shows a 2:2 heterotetramer where the Switch I and Switch II regions of each K-RasG12V interact with both Rgl2RBD molecules. This structural arrangement is highly similar to the H-RasE31K:RALGDS crystal structure and is distinct from the well-characterised Ras:RAFRBD complexes. Importantly, the G12V mutation was found at the dimer interface of K-Ras4BG12V with its partner. Solution state NMR and mass photometry analyses support the heterotetramer formation. Our study reveals a distinct mode of Ras:effector complex formation by RalGEFs, and offers a possible mechanistic explanation for how the oncogenic K-Ras4BG12V hyperactivates the RalA/B pathway.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Competing Interest Statement: The authors declare that they have no conflicts of interest with the contents of this work.
The abstract was edited to be more clear and concise.
