Diverging co-translational protein complex assembly pathways are governed by interface energy distribution

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• Protein-protein interactions are fundamental to cellular function.
• The ribosome acts as a central platform for orchestrating these interactions during protein synthesis.
• Understanding co-translational folding and complex assembly is crucial for cellular processes.

Purpose of the Study:

• To investigate the characteristics governing co-translational protein folding and complex assembly.
• To identify key residues and mechanisms initiating these interactions.
• To explore the link between these mechanisms and human diseases.

Main Methods:

• Selective ribosome profiling
• Imaging techniques
• N-terminomics
• All-atom molecular dynamics simulations
• AlphaFold-Multimer modeling
• Conservation analysis

Main Results:

• Identified specific "hotspot" residues that initiate co-translational assembly upon exposure from the ribosome exit tunnel.
• Demonstrated that these hotspots possess high binding energy and are crucial for interface assembly.
• Revealed that alpha-helices containing hotspots are thermolabile and require partner subunits for stability.
• Showed that mutations in hotspots disrupt co-translational complexation, leading to protein aggregation.
• Found that disease-associated variants in N-terminal acetyltransferases (NATs) disrupt these hotspot clusters.
• Extended findings to other protein complexes, confirming the predictive power of interface energy profiles.

Conclusions:

• Co-translational assembly is initiated by specific, high-affinity "hotspot" residues.
• The stability of these interactions is dynamic and dependent on partner subunits.
• Disruption of these hotspots is linked to protein aggregation and human diseases.
• Interface energy distribution serves as a predictive model for co-translational assembly.