Abstract: Photolyase is a photoenzyme using blue light to repair UV-induced DNA lesions in three life kingdoms. Although earlier studies on microbial photolyases revealed a critical electron-tunneling pathway for the repair mechanism, it is unknown if such electron superexchange can also operate in distant eukaryotic photolyases. Here, using femtosecond spectroscopy we show our systematic dissection of the repair process with seven electron-transfer reactions among ten elementary steps on various photolyases in all life branches. We found a new, unified electron-transfer strategy for all photolyases with bifurcated routes through a conserved structural configuration. Both pathways are operative in repair depending on the relative reduction potentials and converged at damaged-DNA site for efficient repair. From lower microbes to higher eukaryotes, the electron exploits from mainly direct tunneling along one route to dominant two-step hopping on the other path with the same conserved active-site structure through evolution. 

Biosketch: Dongping Zhong received his B.S. in laser physics from Huazhong University of Science and Technology in China and his Ph.D. in Chemical Physics from California Institute of Technology under Ahmed Zewail (1999 Nobel Laureate in Chemistry). For his Ph.D. work, Dr. Zhong received the Herbert Newby McCoy Award and the Milton and Francis Clauser Doctoral Prize from Caltech. He continued his postdoctoral research at Caltech with focus on protein dynamics. In 2002, he joined The Ohio State University as an Assistant Professor and currently he is the Robert Smith Professor of Physics and Professor of Chemistry and Biochemistry. He is a Packard Fellow, Sloan Fellow, Camille Dreyfus Teacher-Scholar, Guggenheim Fellow, APS Fellow, AAAS Fellow, as well as the recipient of the NSF CAREER Award and the OCPA Outstanding Young Researcher Award. He is the committee member in the International July of Physical Science, The L’Oreal-UNESCO awards for Women in Science. His research interests integrate laser spectroscopy and molecular biology to study biomolecular interactions and dynamics, especially DAN-damage repair through longtime collaboration with Aziz Sancar (2015 Nobel Laureate in Chemistry).