Cotranslational protein assembly imposes evolutionary constraints on homomeric proteins

Area of Science:

• Molecular Biology
• Structural Biology
• Biophysics

Background:

• Cotranslational protein folding aids rapid functional structure formation.
• Premature protein complex assembly can occur if interacting nascent chains are close.
• Protein structure analysis reveals homomeric contacts are enriched at C-termini across proteomes.

Purpose of the Study:

• To investigate the evolutionary and mechanistic basis for the observed enrichment of homomeric contacts at polypeptide C-termini.
• To determine if C-terminal positioning of homomeric interfaces enhances assembly efficiency.
• To identify key features governing successful homomer assembly for protein design.

Main Methods:

• Analysis of known protein structures to identify patterns in homomeric contacts.
• High-throughput imaging of protein homomers in Escherichia coli.
• Engineering protein constructs with N- and C-terminal oligomerization domains.
• In vivo, in vitro, and in silico experiments to study assembly dynamics.

Main Results:

• Homomeric protein contacts are significantly enriched toward the C termini of polypeptide chains.
• Proteins with C-terminal homomeric interfaces assemble more efficiently than those with N-terminal interfaces.
• Specific features governing successful homomer assembly were identified.

Conclusions:

• Evolutionary constraints favor C-terminal positioning of homomeric interfaces to ensure folding precedes assembly.
• Optimizing homomer assembly through C-terminal interface design can improve protein expression and facilitate protein design.