Chaperonin overexpression promotes genetic variation and enzyme evolution.

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Biochemistry

Background:

• Protein mutations often decrease stability and are deleterious.
• Chaperones (heat-shock proteins) may buffer mutations, facilitating adaptation.
• The role of chaperonins in buffering destabilizing and adaptive mutations needs further investigation.

Purpose of the Study:

• To investigate the capacity of Escherichia coli GroEL/GroES chaperonins to buffer destabilizing and adaptive mutations.
• To determine if chaperonin overexpression influences the rate of protein evolution and adaptation.

Main Methods:

• In vitro mutational drift experiments were conducted using four different enzymes.
• GroEL/GroES chaperonins were overexpressed to assess their effect on mutation accumulation and protein folding.
• Enzyme variants with mutations in the protein core or significant destabilizing effects were analyzed.

Main Results:

• GroEL/GroES overexpression doubled the number of accumulating mutations.
• Chaperonins promoted the folding of enzyme variants with destabilizing mutations (average >3.5 kcal mol(-1) vs. ~1 kcal mol(-1) without chaperonins).
• Enzymatic specificity divergence occurred significantly faster under GroEL/GroES overexpression, with a higher number of adapted variants showing improved activity (>10-fold).

Conclusions:

• Protein stability is a critical constraint in protein evolution.
• Chaperonins act as key buffering mechanisms, alleviating stability constraints and accelerating adaptive evolution.
• Understanding chaperone function is crucial for comprehending evolutionary processes and protein engineering.