在蛋白质 G B1 域中,盐桥与 lysines 的表征
Jennifer H Tomlinson1, Saif Ullah, Poul Erik Hansen
1Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN UK.
Journal of the American Chemical Society
|March 14, 2009
概括
核磁共振 (NMR) 研究显示,蛋白G中的表面溶酶不形成显著的盐桥,尽管有结晶结构证据. 质子交换率表明碳酸盐催化,而不是盐桥稳定.
科学领域:
- 生物化学 生物化学
- 结构生物学 结构生物学
- 蛋白质动力学 蛋白质动力学
背景情况:
- 蛋白G的B1域拥有六个表面暴露的氨酸残留物.
- 晶体结构始终描绘了其中三种 lysines 形成盐桥,而其他三种没有.
- 研究这些氨酸残留物在蛋白质结构和相互作用中的作用至关重要.
研究的目的:
- 为了阐明氨酸残留在蛋白质G的B1域内的盐桥相互作用中的实际参与.
- 为了协调晶体结构观测和溶液状态蛋白质行为之间的差异.
- 了解pH值和缓冲条件对氨酸-碳酸盐相互作用的影响.
主要方法:
- 核磁共振 (NMR) 光谱被用来研究蛋白质G的B1域.
- 技术包括pH定位,同位素效应测量和15N信号线形状的分析.
- 密度函数理论 (DFT) 的计算用于支持实验结果.
- 使用电位计定位测量充电侧链的pK (a) 值.
主要成果:
- 核磁共振的化学转移和同位素效应表明,氨酸表现为简单的水合胺,不受碳酸盐的pH定位的影响.
- 观察到氨酸NH ((3) ((+) 组的快速内部重定位.
- 测量的pK (a) 值没有显示出盐桥形成的预期扰动,除了E35.
- 在水晶盐桥中涉及的氨酸表现出更快的氨酸质子交换,这表明碳酸盐一般基质催化.
结论:
- 蛋白质G的B1域中的六个表面暴露的溶酶并不显著地参与溶液中的盐桥相互作用.
- 在晶体结构中观察到的盐桥可能不会准确地反映溶液状态.
- 螺旋内E35-K39相互作用显示部分参与,受缓冲条件和静电屏蔽的影响.
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