COSMIC-Linked Ras Mutations at the Interface Between H-Ras and PI3Kγ_RBD Frequently Generate Affinity Increases.

Area of Science:

• Molecular biology
• Cell signaling
• Protein-protein interactions

Background:

• Ras G-proteins (H-, K-, N-Ras) act as molecular switches controlling vital cell pathways.
• The Ras-PI3K-PIP3-PDK-AKT pathway is crucial for immunity and cell growth, often dysregulated in diseases.
• Ras activation depends on binding affinity to PI3K, particularly at the H-Ras:PI3Kγ interface.

Purpose of the Study:

• To investigate evolutionary optimization of the H-Ras:PI3Kγ binding interface for maximal affinity.
• To assess the impact of specific Ras mutations on H-Ras:PI3Kγ binding affinity.

Main Methods:

• Focused on the H-Ras:PI3Kγ co-complex structure and its interfacial residues.
• Introduced 8 conserved interfacial Ras mutations at contact positions.
• Measured changes in H-Ras:PI3Kγ binding affinity for each mutation.

Main Results:

• All 8 introduced Ras mutations altered H-Ras:PI3Kγ binding affinity.
• Four mutations significantly increased affinity, while four significantly decreased it.
• The native interface exhibits intermediate, not maximal, binding affinity.

Conclusions:

• The native H-Ras:PI3Kγ interface has evolved for intermediate affinity, allowing binding plasticity with diverse effectors.
• COSMIC mutations at this interface can increase affinity, with implications for disease mechanisms.
• Findings aid in understanding disease and developing cell biology research tools.