在埃舍里希亚大肠杆菌III类核糖核酸还原酶上,一种具有化学能力的硫硫基
Yifeng Wei1, Guinevere Mathies, Kenichi Yokoyama
1Departments of Chemistry and ‡Biology and §Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, United States.
Journal of the American Chemical Society
|May 16, 2014
概括
第三类核糖核酸减少酶 (RNRs) 使用甲酸盐作为减少剂. 研究人员在大肠杆菌RNR中发现了一种新的硫硫基中间体,揭示了DNA合成和修复的新反应途径.
科学领域:
- 生物化学 生物化学
- 酶学 是一种酶学.
- 分子生物学分子生物学
背景情况:
- 第三类核糖核酸减少酶 (RNRs) 是无氧生物中DNA合成和修复所必需的糖基 (G•) 酶.
- 与其他类型的RNR不同的是,III类RNR传统上使用formate作为减少剂.
研究的目的:
- 调查大肠杆菌III类RNR的反应机制,特别是在没有甲酸盐的情况下.
- 确定反应过程中形成的基因物种,并阐明其在核酸还原中的作用.
主要方法:
- 使用CTP (基质) 和ATP (全质效应剂) 的酶分析与大肠杆菌III类RNR.
- 在同位素标记的蛋白质上进行电子磁共振 (EPR) 谱学 (9.5和140 GHz),以表征基性物种.
- 对反应产物的分析,包括cytidine衍生物和形式依赖的还原.
主要成果:
- 在缺少甲酸盐的情况下,大肠杆菌III类RNR会失去其糖基 (G•) 并形成一种新型的硫基[RSSR2]• (由氨酸稳定的氨基基基).
- 在这个过程中被捕获了一种cytidine衍生物,被提出为3 extquotesingle-keto-deoxycytidine.
- 甲酸盐的添加恢复了G•并减少了cytidine衍生物,表明其在减小半反应中的作用.
结论:
- 这项研究揭示了III类RNR的前所未知的反应途径,其中涉及硫烯基基中间体.
- 这一发现为核酸减少提供了机理性的洞察力,并对理解无氧细菌和古生物中的DNA合成和修复有意义.
- 鉴定到的基机制与其他RNR类提供了相似之处,这表明基在所有RNR类型中都起着保留作用.
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