Coexistence of Different Electron‐Transfer Mechanisms in the DNA Repair Process by Photolyase

Abstract

DNA photolyase has been the topic of extensive studies due to its important role of repairing photodamaged DNA, and its unique feature of using light as an energy source. A crucial step in the repair by DNA photolyase is the forward electron transfer from its cofactor (FADH(-) ) to the damaged DNA, and the detailed mechanism of this process has been controversial. In the present study, we examine the forward electron transfer in DNA photolyase by carrying out high-level ab initio calculations in combination with a quantum mechanical/molecular mechanical (QM/MM) approach, and by measuring fluorescence emission spectra at low temperature. On the basis of these computational and experimental results, we demonstrate that multiple decay pathways exist in DNA photolyase depending on the wavelength at excitation and the subsequent transition. This implies that the forward electron transfer in DNA photolyase occurs not only by superexchange mechanism but also by sequential electron transfer.

Sequential electron transfer governs the UV-induced self-repair of DNA photolesions

“…Limited accessibility of the state crossings is discussed below. As pointed out by Lee and co-workers, 16 the evaluation of diabatic coupling matrix elements (DCMEs) between the electronic states is crucial for proving the validity of a proposed photoreaction mechanism. Our estimates based on the generalized Mulliken Hush and Boys localization approaches, 77 , 78 yielded DCMEs exceeding 0.1 eV between the consecutive electronic states.…”

Anion photoelectron spectroscopy of protein chromophores

“…For deprotonated chromophore anions, electron emission is another common relaxation process. Photoinduced electron emission is a ubiquitous phenomenon in biology; a particularly well-known example is the repair mechanism for photodamaged DNA, which involves photoinduced electron transfer from the electronically excited cofactor of DNA photolyase, flavin adenine dinucleotide (FADH − ) [7]. [8].…”

An Ethenoadenine FAD Analog Accelerates UV Dimer Repair by DNA Photolyase

“…The same arguments can be made if Ade is replaced by ε‐Ade. However, even though the reduction potential of the CPD is ‐1.96V vs NHE , a coexistence of one‐step (superexchange) and two‐step (hopping) mechanisms may be possible . An examination of the reduction potentials of the reaction partners is a reasonable first step in addressing this question.…”