Disulfide bonds are generated by quinone reduction

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Disulfide bond formation is crucial for protein folding and function.
• The origin of disulfide bonds in vivo remains largely unknown.
• Existing knowledge focuses on disulfide exchange, not de novo bond generation.

Purpose of the Study:

• To investigate the de novo origin of disulfide bonds.
• To characterize the enzymatic activity of DsbB in disulfide bond formation.
• To elucidate the role of quinones in disulfide bond generation.

Main Methods:

• Development of a novel assay to study disulfide bond formation.
• In vitro reconstitution of oxidative folding using DsbA, DsbB, and quinones.
• Characterization of quinone reduction during the reaction.
• Assessment of ribonuclease A refolding and DsbC requirement.

Main Results:

• DsbB utilizes quinones to generate disulfide bonds de novo.
• This DsbB-quinone activity is identified as a major source of disulfides in vivo.
• The DsbA-DsbB-quinone system catalyzes oxidative refolding of ribonuclease A.
• DsbC is required for regaining ribonuclease activity, indicating non-native disulfide bonds.

Conclusions:

• DsbB possesses a novel catalytic activity involving quinone reduction for disulfide bond generation.
• The DsbA-DsbB-quinone system is essential for oxidative folding in vivo.
• Kinetic isolation of oxidative and isomerase pathways prevents cellular oxidative damage.