基酶P集群的氧依赖性转移稳定性
Hannah L Rutledge1, Jonathan Rittle1, Laura M Williamson1
1Department of Chemistry and Biochemistry , University of California, San Diego , 9500 Gilman Drive , La Jolla , California 92093-0356 , United States.
Journal of the American Chemical Society
|June 1, 2019
概括
在没有氧联体的情况下氧化时,酸酶中的P可以失去铁原子,但仍然减少. 这种可变性是酶功能中电子转移的关键.
科学领域:
- 生物化学
- 生物有机化学
- 酶机制
背景情况:
- 酸酶促进二 (N2) 转化为氨 (NH3),这是生命的重要过程.
- 电子转移到活性位子辅助因子 (FeMoco) 涉及铁蛋白 (MoFeP) 中的 [8Fe-7S] 集群 (P-集群).
- P集群表现出形状灵活性,在氧化时发生结构变化,涉及氧联体 (Ser或Tyr) 并影响电子转移.
研究的目的:
- 研究氧联体在Azotobacter vinelandii (Av) MoFeP的P集群中的作用.
- 确定消除或改变氧联体如何影响P稳定性和酶活性.
- 将AvMoFeP中的P群环境与Gluconacetobacter diazotrophicus (Gd) MoFeP的环境进行比较.
主要方法:
- 位点定向的突变产生AvMoFeP变体:βSer188Ala (没有氧联体),βPhe99Tyr/βSer188Ala (类似Gd的环境) 和βPhe99Tyr (两个氧联体).
- 生物化学测试以评估酶的活性.
- 用光谱和结构分析来描述P星团的稳定性和组成.
主要成果:
- 在没有氧联体的情况下,P集群在氧化时变得结构不稳定,可逆地失去Fe中心.
- 缺乏氧联体的变种保留了野生类型的二降解活性.
- Av和Gd MoFePs对Ser和Tyr配体有明显的偏好,这表明它们具有特定的进化适应性.
结论:
- P 集群的组成不稳定性,特别是缺少氧联体,对于使多电子反应成为可能的氧化还原连接构造变化至关重要.
- 在MoFeP中氧联体的结构控制超出了直接的协调范围.
- 可变的Fe-S集群可能是金属酶中复杂的氧化还原过程的一般特征.
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