适应性约束的直接演示
Stephen P Miller1, Mark Lunzer, Antony M Dean
1BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA.
Science (New York, N.Y.)
|October 21, 2006
概括
贝塔-异甲酸脱酶 (IMDH) 的定向进化揭示了酶约束,如辅因子抑制,塑造了适应性进化. 这些局限性解释了为什么工程酶对尼古丁胺胺氨基二核酸 (NADP) 产生较低的亲和力.
科学领域:
- 生物化学 生物化学
- 进化生物学 进化生物学
- 酶工程是指酶工程的工程.
背景情况:
- 进化约束在塑造适应的作用仍然不完全理解.
- β-异甲酸脱酶 (IMDH) 自然使用尼古丁胺二核酸 (NAD),但可以根据尼古丁胺二核酸 (NADP) 的特异性进行工程.
- 了解酶进化需要检查适应性景观和固有的局限性.
研究的目的:
- 调查酶制约对工程IMDH适应性进化的影响.
- 为了确定观察到的进化结果是否与理论适应性景观的预测保持一致.
- 阐明在酶进化中选择和约束之间的相互作用.
主要方法:
- 使用定向进化来改变工程IMDH的协酶特异性,从NAD变成NADP.
- 测量了对NADP和NADPH的突变酶亲和力.
- 观察到的进化轨迹与包含已知的酶制约因素的模型进行了分析.
主要成果:
- 设计的IMDH始终对NADP产生较低的亲和力,这是对减少NADPH抑制的选择的相关反应.
- 这一结果与适应性景观相一致,受限于最大周转率 (kcat),NADP/NADPH亲和关系以及NAD/NADP使用权衡.
- 高细胞内NADPH水平和蛋白质合成成本进一步加强了NAD的使用.
结论:
- 进化约束极大地影响了适应性进化的方向和结果.
- 通过酶限制定义的适应性景观对于理解酶进化至关重要.
- 选择性压力与固有的约束相互作用,产生可预测的进化模式.
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