Low protein expression enhances phenotypic evolvability by intensifying selection on folding stability.

Area of Science:

• Evolutionary biology
• Protein engineering
• Molecular biology

Background:

• Protein abundance influences genotype evolution but its effect on phenotype evolution is unclear.
• Green fluorescent protein (GFP) is a model system for studying protein evolution.

Purpose of the Study:

• To investigate the role of protein abundance in the evolvability of green fluorescent protein (GFP).
• To understand how protein expression levels impact the evolution of novel phenotypes, specifically cyan fluorescence.

Main Methods:

• Evolving GFP in E. coli through multiple cycles of mutation and selection.
• Utilizing a computational model to predict evolutionary dynamics.
• Experimentally testing model predictions.

Main Results:

• Low GFP expression significantly facilitates the evolution of cyan fluorescence.
• Computational modeling and experimental validation revealed that lowly expressed proteins are under stronger selection for proper folding.
• A synergy between protein scarcity and stability was observed, promoting evolvability.

Conclusions:

• Low protein abundance enhances protein evolvability by increasing selection for stability and proper folding.
• The observed scarcity-stability synergy may be a widespread mechanism for evolving new protein functions.
• This finding has implications for protein engineering and synthetic biology.