Synonymous and non-synonymous codon substitutions can alleviate dependence on GroEL for folding.

Area of Science:

• Molecular Biology
• Protein Folding
• Chaperone Proteins

Background:

• The Escherichia coli GroEL/ES chaperonin system is crucial for ATP-driven protein folding.
• While GroEL/ES assists many proteins in vitro, only fewer than 100 are obligate clients in E. coli.
• The specific features differentiating obligate clients remain largely unknown.

Purpose of the Study:

• To investigate the molecular determinants that distinguish obligate clients of the GroEL/ES chaperonin system.
• To identify features of proteins that reduce their dependence on GroEL/ES for proper folding.

Main Methods:

• Developed a system to select mutations in mouse dihydrofolate reductase (mDHFR) that decrease its GroEL/ES dependence.
• Analyzed both synonymous and non-synonymous codon substitutions in mDHFR.
• Employed computational analysis to assess the impact of synonymous substitutions on translation rates.

Main Results:

• Both synonymous and non-synonymous codon substitutions in mDHFR significantly reduced its dependence on GroEL/ES.
• Non-synonymous mutations enhanced the rate of spontaneous protein folding.
• Synonymous substitutions were computationally predicted to influence translation rates at specific points.

Conclusions:

• Protein folding efficiency and translation dynamics are key factors influencing dependence on chaperonin systems like GroEL/ES.
• Understanding these factors can help elucidate the criteria for obligate client proteins.
• This study provides a framework for dissecting chaperonin-client specificity.