Protein folding drives disulfide formation

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Folding

Background:

• Protein disulfide isomerase (PDI) is crucial for the oxidative folding of proteins containing disulfide bonds.
• The precise reaction sequence by which PDI achieves native protein oxidation remains incompletely understood.

Purpose of the Study:

• To develop a novel technique for simultaneously measuring disulfide bond formation and protein folding.
• To elucidate the role of PDI in the oxidative folding pathway and identify mechanisms preventing misfolding.

Main Methods:

• Development of a technique allowing independent quantification of disulfide formation and protein folding kinetics.
• Analysis of early and late stages of the oxidative folding pathway.

Main Results:

• Non-native disulfide bonds form early in the folding process and can lead to protein misfolding.
• Specific PDI domains promote the formation of native disulfide bonds during the later stages of folding.
• A model for cotranslational oxidative folding is proposed, where PDI acts as a transient factor released upon substrate folding.

Conclusions:

• PDI's function is stage-specific, favoring native disulfide bonds late in folding to ensure correct protein structure.
• The proposed cotranslational oxidative folding mechanism provides a general explanation for PDI's activity across diverse protein substrates.