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Dynamics and mechanism of repair of ultraviolet-induced (6-4) photoproduct by photolyase

机译：光解酶修复紫外线诱导的（6-4）光产物的动力学及其机理

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摘要

One of the detrimental effects of ultraviolet radiation on DNA is the formation of the (6-4) photoproduct, 6-4PP, between two adjacent pyrimidine rings. This lesion interferes with replication and transcription, and may result in mutation and cell death2. In many organisms, a flavoenzyme called photolyase uses blue light energy to repair the 6-4PP (ref. 3). 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 picoseconds, but surprisingly fast back electron transfer in 50 picoseconds without repair. 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 picoseconds 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.
机译：紫外线对DNA的有害影响之一是在两个相邻的嘧啶环之间形成（6-4）光产物6-4PP。该病变会干扰复制和转录，并可能导致突变和细胞死亡2。在许多生物中，一种称为光裂解酶的黄素酶利用蓝光能量修复6-4PP（参考文献3）。修复反应的分子机理了解甚少。在本文中，我们使用超快光谱法显示了修复光循环的关键步骤是酶与底物之间的循环质子转移。通过飞秒使酶动力学与修复功能同步，我们跟踪了功能演化并观察到直接电子转移从激发的黄素辅因子到225皮秒内的6-4PP，但出人意料的是在50皮秒内快速返电子转移而无需修复。我们发现，活性位点中的组氨酸残基和6-4PP之间的催化质子转移是由最初的光诱导电子从激发的黄素辅因子转移至6-4PP引起的，发生在425皮秒内，并导致6-4PP的修复。数十纳秒。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。

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  • 来源
    《Nature》 |2010年第7308期|P.887-890|共4页
  • 作者

    Jiang Li; Zheyun Liu; Chuang Tan; Xunmin Guo; Lijuan Wang; Aziz Sancar; Dongping Zhong;

  • 作者单位

    Departments of Physics, Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics and Biochemistry, 191 West Woodruff Avenue, The Ohio State University, Columbus, Ohio 43210, USA;

    rnDepartments of Physics, Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics and Biochemistry, 191 West Woodruff Avenue, The Ohio State University, Columbus, Ohio 43210, USA;

    rnDepartments of Physics, Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics and Biochemistry, 191 West Woodruff Avenue, The Ohio State University, Columbus, Ohio 43210, USA;

    rnDepartments of Physics, Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics and Biochemistry, 191 West Woodruff Avenue, The Ohio State University, Columbus, Ohio 43210, USA;

    rnDepartments of Physics, Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics and Biochemistry, 191 West Woodruff Avenue, The Ohio State University, Columbus, Ohio 43210, USA;

    rnDepartment of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA;

    rnDepartments of Physics, Chemistry and Biochemistry, Programs of Biophysics, Chemical Physics and Biochemistry, 191 West Woodruff Avenue, The Ohio State University, Columbus, Ohio 43210, USA;

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