2014.3.18 Dynamics and Mechanism of Ultraviolet-damaged DNA Repair by Photolyase
Dynamics and Mechanism of Ultraviolet-damaged DNA Repair byPhotolyase
Dongping Zhong, Ph.D.
Robert Smith Professor, Dept of Physics
Professor,Dept of Chemistry and Biochemistry
Photolyase uses blue light to restore the major ultraviolet(UV)-induced DNA damage, the cyclobutane pyrimidine dimer (CPD) and (6-4)photoproduct (6-4PP), but the detailed repair mechanisms are not known. Here, weuse femtosecond spectroscopy to show the entire mapping of repair evolution inreal time by capturing all elementary reaction steps from initial reactants, tovarious intermediates and to final products. For example, we observed that theCPD splits in two sequential steps within 90 ps and the electron tunnels betweenthe cofactor and substrate through a remarkable route with an interveningadenine. Various site-directed mutations reveal that the active-site residuesare critical to achieving high repair efficiency through a unique electrostaticenvironment by optimizing the redox potentials and local flexibility, and thusbalance all catalytic reactions to maximize enzyme activity. These key findingsreveal the complete spatio-temporal molecular picture of CPD and 6-4PP repair byphotolyase and elucidate the underlying molecular mechanisms and their repairphotocycles.