The chaperonin cycle and protein folding

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Protein folding is crucial for cellular function.
• Molecular chaperones non-covalently assist protein folding, enhancing active protein yields.
• The exact mechanisms of molecular chaperone action remain largely unknown.

Purpose of the Study:

• To elucidate the mechanism of action for the molecular chaperone Cpn60 (GroEL).
• To investigate the role of the co-chaperone Cpn10 (GroES) in the Cpn60-mediated folding process.

Main Methods:

• The study focuses on experimental observations of the Cpn60/Cpn10 system.
• Analysis of the binding and release cycles of unfolded protein substrates and co-chaperones.
• Investigating the effects of co-chaperones and unfolded proteins on the Cpn60 complex's nucleotide-bound states.

Main Results:

• The folding reaction is driven by cycles of binding and release involving Cpn10 (GroES) and unfolded protein substrates.
• Cpn10 stabilizes the ADP-bound state of Cpn60, while unfolded proteins stimulate ADP-ATP exchange.
• These cycles facilitate substrate protein release into the Cpn60 complex cavity for folding, preventing aggregation.

Conclusions:

• A model is proposed where substrate proteins undergo multiple binding and release cycles within the Cpn60 complex.
• This process allows for folding in a protected environment, free from interactions with other folding intermediates.
• Cpn60 proteins enhance protein folding by effectively blocking aggregation pathways.