Cao Xiaodan, Yan Luyao, Yang Chao, Wang Lijuan, Zhang Meng, Zhong Dongping
Center for Ultrafast Science and Technology, School of Chemistry and Chemical Engineering, Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University, Shanghai 200240, China.
Center for Ultrafast Science and Technology, School of Physics and Astronomy, Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University, Shanghai 200240, China.
J Am Chem Soc. 2025 Apr 2;147(13):11291-11300. doi: 10.1021/jacs.4c18557. Epub 2025 Mar 19.
The class-II photolyases (PLs) are distantly related to the microbial class-I photolyases with low sequence similarity, yet they maintain a similar structural topology and repair the same UV-induced cyclobutane pyrimidine dimer (CPD). The class-I photolyases have been well characterized through a direct electron-transfer (ET) tunneling mechanism with high repair quantum yield, but such a mechanism seemingly does not apply to all of the members in the diversified photolyase family. Here, using femtosecond spectroscopy, we show our systematic characterization of CPD repair by the class-II photolyases from and and reveal their complete photocycles with determination of reaction times of all ten elementary steps, including seven electron-transfer processes. We found that the initial electron injection bifurcates along two parallel routes, direct tunneling and two-step hopping. Unlike the class-I photolyases, the direct tunneling process here is significantly slower, occurring in several nanoseconds. This slow tunneling route leads to shifting of the branching yield toward the intrinsic two-step hopping pathway through the adenine intermediate. Throughout the photolyase family, the enzymes have adopted a unified bifurcating electron-transfer strategy as a universal repair mechanism through evolution.
