Photoreactivation of DNA by an archaeal nucleoprotein Sso7d
Photoreactivation of DNA by an archaeal nucleoprotein Sso7d
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DOI：
10.1073/pnas.0603484103
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发表时间：
2006-11-07
影响因子：
11.1
通讯作者：
Sugiyama, Hiroshi
中科院分区：
文献类型：
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作者：
Tashiro, Ryu;Wang, Andrew H-J.;Sugiyama, Hiroshi
Sso 7 d是一种极端嗜热菌的染色体蛋白。Sso 7 d-d（GTAAT（1）UAC）（2）的晶体结构已在高分辨率下澄清，表明该蛋白质结合在DNA的小沟中，导致约60度的尖锐扭结。最近，我们发现Sso 7 d和含5-碘尿嘧啶-（U-1）-的5 '-d（GTAAT（1）UAC）-3'的光照射有效地诱导了T-5在扭折处的甲基上的氢的夺取。在本研究中，我们发现含5-溴尿嘧啶（U-Br）的5 '-d（GTAAT（Br）UAC）-3'的光反应性在Sso 7 d的存在下增强。使用含次黄嘌呤（I）的5 ′-d（ITAAT（Br）UAC）-3 ′，我们证明了从Sso 7 d到DNA的电子转移有效地发生。产物分析显示，位于DNA表面的Sso 7 d的Trp-24在光照射期间被消耗以产生N '-甲酰犬尿氨酸，表明Trp-24充当电子源。为了探索Sso 7 d与其他DNA底物之间电子转移的可能性，我们检测了Sso 7 d对胸腺嘧啶二聚体5 '-d（GTAAT TAC）-3'的光化学修复。Sso 7 d在辐射条件下有效地将5 '-d（GTAATTAC）-3'修复为5 '-d（GTAATTAC）-3'。在此反应期间，Trp-24未被显著氧化，表明修复的TT序列的阴离子自由基被Trp-24的阳离子自由基氧化，并且在此系统中运行所谓的“循环电子转移”机制。
Sso7d is a chromosomal protein of hyperthermophilic Archaea. The crystal structure of Sso7d-d(GTAAT(1)UAC)(2) has been clarified at high resolution, showing that the protein binds in the minor groove of DNA, causing a sharp kink of approximate to 60 degrees. Recently, we found that photoirradiation of Sso7d and 5-iodouracil-(U-1)-containing 5'-d(GTAAT(1)UAC)-3' efficiently induced the abstraction of hydrogen from the methyl group of T-5 at the kink. In the present study, we found that the photoreactivity of 5-bromouracil (U-Br)-containing 5'-d(GTAAT(Br)UAC)-3' was enhanced in the presence of Sso7d. Using hypoxanthine (I)-containing 5'-d(ITAAT(Br)UAC)-3', we demonstrated that electron transfer occurs efficiently from Sso7d to DNA. Product analysis showed that Trp-24 of Sso7d, located at the surface of the DNA, is consumed to produce N'-formylkynurenine during photoirradiation, indicating that Trp-24 acts as an electron source. To explore the possibility of electron transfer between Sso7d and other DNA substrates, we examined the photochemical repair of the thymine dimer 5'-d(GTAAT TAC)-3' by Sso7d. Sso7d effectively repaired 5'-d(GTAAT TAC)-3' to 5'-d(GTAATTAC)-3' under irradiation conditions. During this reaction, Trp-24 was not oxidized significantly, indicating that the anion radical of the repaired TT sequence is oxidized by the cation radical of Trp-24, and that a so-called "circular electron transfer" mechanism is operating in this system.