Dynamics and mechanism of repair of ultraviolet-induced (6-4) photoproduct by photolyase.
Dynamics and mechanism of repair of ultraviolet-induced (6-4) photoproduct by photolyase.
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作者：
紫外线辐射对DNA的有害影响之一是在两个相邻的嘧啶之间形成（6-4）光产物（6-4PP）。这种病变干扰复制和转录，并可能导致突变和细胞死亡。在许多生物体中，一种叫做光解酶的黄酶利用蓝光能量来修复6-4PP。修复反应的分子机制尚不清楚。在这里，我们使用超快光谱来证明修复光循环的关键步骤是酶和底物之间的循环质子转移。通过飞秒同步的酶动力学与修复功能，我们观察了功能的演变，并观察到电子在225秒内从激活的黄素辅因子直接转移到6-4PP，而在50秒内发生了惊人的反向电子转移。引人注目的是，我们发现活性位点组氨酸残基和6-4PP之间的催化质子转移是由激发的黄素辅助因子向6-4PP的初始光诱导电子转移引起的，发生在425 ps内，并在几十纳秒内导致6-4PP修复。这些关键动力学定义了修复光循环，并解释了酶适度效率的潜在分子机制。
One of the detrimental effects of UV radiation on DNA is the formation of the (6-4) photoproduct (6-4PP) between two adjacent pyrimidines. This lesion interferes with replication and transcription and may result in mutation and cell death. In many organisms a flavoenzyme called photolyase uses blue light energy to repair the 6-4PP. The molecular mechanism of the repair reaction is poorly understood. Here, we use ultrafast spectroscopy to show that the key step in the repair photocycle is a cyclic proton transfer between the enzyme and the substrate. By femtosecond synchronization of the enzymatic dynamics with the repair function, we followed the function evolution and observed direct electron transfer from the excited flavin cofactor to the 6-4PP in 225 ps but surprisingly fast back electron transfer in 50 ps without repair. Strikingly, we found that the catalytic proton transfer between a histidine residue in the active site and the 6-4PP, induced by the initial photoinduced electron transfer from the excited flavin cofactor to 6-4PP, occurs in 425 ps and leads to 6-4PP repair in tens of nanoseconds. These key dynamics define the repair photocycle and explain the underlying molecular mechanism of the enzyme’s modest efficiency.
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DOI：
10.1073/pnas.0809180106
发表时间：
2009-04-28
影响因子：
11.1
作者：
Hitomi, Kenichi;DiTacchio, Luciano;Getzoff, Elizabeth D.
通讯作者：
Getzoff, Elizabeth D.
影响因子：
15
作者：
Kao, Ya-Ting;Tan, Chuang;Zhong, Dongping
通讯作者：
Zhong, Dongping
影响因子：
4.8
作者：
Hitomi, K;Kim, ST;Todo, T
通讯作者：
Todo, T
影响因子：
3.3
作者：
Li, Jiang;Uchida, Takeshi;Kitagawa, Teizo
通讯作者：
Kitagawa, Teizo
影响因子：
4.8
作者：
Schleicher, Erik;Hitomi, Kenichi;Weber, Stefan
通讯作者：
Weber, Stefan