Dynamics and mechanism of cyclobutane pyrimidine dimer repair by DNA photolyase
Dynamics and mechanism of cyclobutane pyrimidine dimer repair by DNA photolyase
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DOI：
10.1073/pnas.1110927108
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发表时间：
2011-09-06
影响因子：
11.1
通讯作者：
Zhong, Dongping
中科院分区：
文献类型：
--
作者：
Liu, Zheyun;Tan, Chuang;Zhong, Dongping
Photolyase使用蓝光通过分裂环丁烷环将主要的紫外线（UV）诱导的DNA损伤（环丁烷嘧啶二聚体（CPD））恢复为两个正常碱基。我们早期的研究表明，通过循环电子转移自由基机制，在700 ps内完成整体修复。然而，两个基本的过程，电子隧穿途径和环丁烷环分裂，没有得到解决。在这里，我们使用超快紫外吸收光谱显示，CPD分裂在两个连续的步骤内90 ps和电子隧道之间的辅因子和基板通过一个显着的路线与干预腺嘌呤。定点突变表明，活性位点残基是实现高修复效率，独特的静电环境，以优化氧化还原电位和局部灵活性，从而平衡所有催化反应，以最大限度地提高酶活性的关键。这些关键发现揭示了光裂合酶修复CPD的完整时空分子图像，并阐明了该酶高修复效率的潜在分子机制。
Photolyase uses blue light to restore the major ultraviolet (UV)-induced DNA damage, the cyclobutane pyrimidine dimer (CPD), to two normal bases by splitting the cyclobutane ring. Our earlier studies showed that the overall repair is completed in 700 ps through a cyclic electron-transfer radical mechanism. However, the two fundamental processes, electron-tunneling pathways and cyclobutane ring splitting, were not resolved. Here, we use ultra-fast UV absorption spectroscopy to show that the CPD splits in two sequential steps within 90 ps and the electron tunnels between the cofactor and substrate through a remarkable route with an intervening adenine. Site-directed mutagenesis reveals that the active-site residues are critical to achieving high repair efficiency, a unique electrostatic environment to optimize the redox potentials and local flexibility, and thus balance all catalytic reactions to maximize enzyme activity. These key findings reveal the complete spatio-temporal molecular picture of CPD repair by photolyase and elucidate the underlying molecular mechanism of the enzyme's high repair efficiency.