Determining complete electron flow in the cofactor photoreduction of oxidized photolyase

• DOI: 10.1073/pnas.1311073110
• Publication Date: 2013-07-24T17:32:58Z
• Authors: Zheyun Liu; Chuang Tan; Xunmin Guo; Jiang Li; Lijuan Wang; Aziz Sancar; Dongping Zhong
• Keywords: Photolyase; Flavin adenine dinucleotide; Electron donor

The flavin cofactor in photoenzyme photolyase and photoreceptor cryptochrome may exist an oxidized state should be converted into reduced state(s) for biological functions. Such redox changes can efficiently achieved by photoinduced electron transfer (ET) through a series of aromatic residues the enzyme. Here, we report our complete characterization photoreduction dynamics with femtosecond resolution. With various site-directed mutations, identified all possible donors enzyme determined their ET timescales. excited behaves as sink to draw flow from encircling molecules three distinct layers active site center protein surface. dominant follows conserved tryptophan triad hopping pathway across multiple tunneling steps. These occur ultrafast less than 150 ps are strongly coupled local solvent relaxations. reverse is slow nanosecond range ensure high reduction efficiency. 12 experimentally elementary steps 6 reaction pairs, exhibits reduction–potential gradient along same favorable reorganization energies drive highly unidirectional toward active-site