Distinct Binding Preferences Between Ras and Raf Family Members and the Impact on Oncogenic Ras Signaling by Terrell et al

This study examines the ability of individual Ras and Raf proteins to interact in live cells using bioluminescence resonance energy transfer (BRET) technology. The BRET system allows quantitative measurements to be obtained under conditions that preserve crucial features of Ras and Raf regulation, including lipid processing, intracellular trafficking, membrane microdomain targeting, and protein phosphorylation.

Strikingly, our findings demonstrate pronounced binding preferences between the Ras and Raf family members. We find that while C-Raf and K-Ras can bind with high affinity to all Ras or Raf family members respectively, H-Ras displays preferential binding to C-Raf whereas B-Raf exhibits a striking selectivity for K-Ras. The B-Raf selectivity is mediated by the acidic, N-terminal segment of B-Raf and requires the K-Ras polybasic region for high-affinity binding.