DNA聚合酶β催化:不同的机制是可能的吗?
Ian L Alberts1, Yanli Wang, Tamar Schlick
1Department of Chemistry and Courant Institute of Mathematical Sciences, 251 Mercer Street, New York University, New York, New York 10012, USA.
Journal of the American Chemical Society
|August 19, 2007
概括
研究人员使用QM/MM.研究了DNA聚合酶β (polβ) 机制. 核酸转移的最可能的途径涉及初始去质子化到水,对不匹配的基对有更高的能量障碍,解释了聚合酶忠实性.
科学领域:
- 生物化学和分子生物学
- 计算化学计算化学
背景情况:
- DNA聚合酶对于DNA复制和修复是必不可少的.
- 在原子层面理解DNA聚合酶机制是解释忠实性的关键.
- 哺乳动物DNA聚合酶β (polβ) 是一个模型X系聚合酶.
研究的目的:
- 研究聚β中核酸转移的低能途径.
- 为了比较正确 (G:C) 与不正确 (G:G) 基配对的反应机制.
- 阐明酶环境和溶剂在反应真实性中的作用.
主要方法:
- 使用混合量子力学/分子力学 (QM/MM) 技术.
- 采用受约束的能源最小化协议.
- 模拟了反应核心,酶环境和明确的溶剂效应.
主要成果:
- 最可能的初始步骤是去质子化为水,其次是质子迁移,激活能量为~15 kcal/mol.
- 直接向核酸或活性位点Asp残留物脱质,在能量方面不那么有利.
- 确定速率的步骤是初始去质子化与核友攻击相结合.
- 由于扭曲,不匹配的G:G配对表现出比G:C配对高5kcal/mol的激活能量.
结论:
- 这些发现支持了DNA聚合酶功能的现有机制.
- 通过水分子的初始去质子化是聚β核酸转移中的关键步骤.
- 活性位点预组织影响了聚合酶家族的核酸特异性和忠实性.
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