Visualizing the DNA repair process by a photolyase at atomic resolution.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Photolyases are flavoproteins that use blue light to repair DNA photolesions.
• Understanding the repair mechanism is crucial for DNA repair research.

Purpose of the Study:

• To elucidate the structural mechanism of photolyase-catalyzed cyclobutane pyrimidine dimer (CPD) repair.
• To visualize the complete enzymatic catalysis at atomic resolution across a wide timescale.

Main Methods:

• Time-resolved serial femtosecond crystallography (TR-SFX) was employed to capture reaction intermediates.
• 18 time-dependent snapshots were obtained, detailing changes in four reaction loci.
• A molecular movie of the CPD repair process was generated.

Main Results:

• The study captured CPD lesion repair in the picosecond-to-nanosecond range.
• Enzyme recovery and formation of the reduced enzyme-product complex were observed at 500 nanoseconds.
• Back-flip intermediates of thymine bases were captured at 25 to 200 microseconds, showing DNA reannealing.

Conclusions:

• The complete molecular mechanism of photolyase action, including chemistry and catalysis, was determined.
• The findings provide atomic-level insights into DNA repair dynamics.
• This work advances our understanding of flavoprotein function in DNA repair.