硫酸盐和酸盐运输蛋白中的氧化离子选择性:一项ab initio/CDM研究
1Contribution from the Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan, R.O.C.
Journal of the American Chemical Society
|August 19, 2004
概括
硫酸盐和酸盐运输蛋白通过溶解处罚和结合口袋大小的差异来实现离子选择性. 这些因素解释了为什么ModA与酸盐结合,SBP与硫酸盐结合,同时避免带电氨基酸.
科学领域:
- 生物化学 生物化学
- 分子生物学分子生物学
- 计算化学计算化学
背景情况:
- 硫酸盐 (SO ((4) ((2-)) 和酸盐 (MoO ((4) ((2-)) 运输蛋白对于各自的离子具有显著的选择性,尽管它们在电荷,几何和结合性质方面具有相似之处.
- 了解这种离子歧视的分子基础对于阐明运输机制和蛋白质进化至关重要.
研究的目的:
- 通过计算来研究离子-溶剂相互作用,离子-氨基酸相互作用和结合口袋大小对硫酸盐和酸盐运输蛋白中的离子选择性的贡献.
- 确定SBP和ModA对硫酸盐的偏好与酸盐/酸盐的偏好相关的能量因素.
主要方法:
- 利用量子力学/连续介电方法来计算自由能量.
- 模拟硫酸盐结合部位,使用不同的溶剂暴露,以模拟硫酸盐与酸盐/酸盐的替代.
- 分析了结合口袋大小和氨基酸成分对阳离子结合的影响.
主要成果:
- 酸盐 (MoO(4)(2-)) 运输蛋白 (例如,ModA) 优先结合酸盐/酸盐 (WO(4)(2-)) 由于较低的溶解处罚和较大的,刚性结合腔减弱了硫酸盐 (SO(4)(2-)) 相互作用.
- 硫酸盐 (SO ((4) ((2-)) 运输蛋白 (例如,SBP) 偏好硫酸盐,因为它具有小的结合口袋,可以在固态上阻碍较大的酸盐/酸盐离子.
- 在SBP和ModA结合点中没有充电残留物 (Lys/Arg),可以防止过度稳定,从而在运输过程中有效释放离子.
结论:
- 硫酸盐和酸盐载体中的阳离子选择性主要由溶解能量和结合口袋的物理约束决定.
- 从结合点中进化排除带电残留物优化了离子运输的动态过程.
- 这些发现提供了分子层面的了解,在生物系统中的离子歧视.
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