在Zn-myoglobin和细胞染色体b之间进行动态对接和电子转移(5)
Zhao-Xun Liang1, Judith M Nocek, Kai Huang
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Journal of the American Chemical Society
|June 13, 2002
概括
在肌球蛋白 (Mb) 上的中和电荷显著增强了电子转移 (ET) 与细胞染色体b5 (cyt b5),而不会改变结合亲和力. 这揭示了"动态对接"模型,其中反应性和结合性脱,对生物过程至关重要.
科学领域:
- 生物化学 生物化学
- 生物物理学的生物物理.
- 蛋白相互作用 蛋白相互作用
背景情况:
- 蛋白质之间的电子转移 (ET) 对生物过程至关重要.
- 肌红蛋白 (Mb) 和细胞染色体b5 (cyt b5) 相互作用对于氧气运输和新陈代谢至关重要.
- 了解影响蛋白质-蛋白质相互作用和ET的因素是阐明细胞机制的关键.
研究的目的:
- 研究中和负电荷对Mb酸对其与细胞b5.5的相互作用和ET的影响.
- 探索如何修改Mb的环境影响结合亲和和ET率.
- 阐明电子转移反应中蛋白质与蛋白质相互作用的机制.
主要方法:
- 采用替代肌球蛋白 (ZnMb) 与修饰的血 propionates (diester 和 diamide) 来中和电荷.
- 在不同的pH值和离子强度上测量了光启动ET速率.
- 采用异热定位热度计 (ITC) 和NMR光谱来评估结合和形状变化.
- 执行布朗动力学 (BD) 模拟和ET路径计算.
主要成果:
- 电荷中和的Mb酸盐增加了第二阶ET速率常数与细胞b5多达几百倍.
- 尽管进行了修改,但ZnMb和cyt b5之间的结合亲和力基本保持不变.
- 核磁共振研究显示,Mb heme口袋的形状变化很小.
- BD模拟支持了一个"动态对接"模型,其中许多弱相互作用,而不是强大的结合,促进ET.
结论:
- 基酸的中和增强了ET与细胞b5的反应性,而不会影响结合亲和力.
- 结果支持"动态对接"范式,将结合亲和关系与ET活动脱.
- 这一发现对生物体内涉及Mb和血红蛋白 (Hb) 的氧化还原过程具有显著的生理影响.
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