The RAS-Effector Interface: Isoform-Specific Differences in the Effector Binding Regions

Area of Science:

• Molecular biology
• Biochemistry
• Structural biology

Background:

• RAS proteins are key regulators of intracellular signaling pathways.
• RAS effector interactions are crucial for transmitting extracellular signals.
• A comprehensive understanding of RAS-effector molecular interactions remains incomplete.

Purpose of the Study:

• To investigate structure-function relationships in RAS-effector interactions.
• To systematically analyze binding affinities and identify critical interaction determinants.
• To provide new insights into the molecular recognition mechanisms between RAS proteins and their effectors.

Main Methods:

• In vitro binding assays using fluorescence polarization to determine equilibrium dissociation constants.
• In silico analysis combining in vitro data with crystal structure information.
• Construction of an interaction matrix to identify critical interaction hotspots.

Main Results:

• Quantified binding affinities for HRAS, KRAS, NRAS, RRAS1, and RRAS2 with various RAS binding (RB) and RAS association (RA) domains.
• Identified interaction hotspots critical for RAS-effector binding.
• Dissected hotspots into five distinct regions (R1-R5), revealing conserved and variable elements across effectors.
• Proposed intermolecular β-sheet interaction in R1 as a central recognition region and R3 for isoform-specific contacts.

Conclusions:

• RAS-effector interactions are governed by specific molecular determinants within RB/RA domains.
• The R1 region, via β-sheet interactions, plays a central role in RAS recognition.
• The R3 region contributes to the specificity of interactions between RAS and RRAS isoforms and their effectors.