一个表皮性子限制了葡萄糖皮质体受体进化的方向
Jamie T Bridgham1, Eric A Ortlund, Joseph W Thornton
1Center for Ecology and Evolutionary Biology, University of Oregon, Eugene, Oregon 97403, USA.
Nature
|September 26, 2009
概括
蛋白质功能的进化变化,如葡萄糖皮质体受体中的激素特异性,可以变得不可逆转. 随后的突变优化了新的功能,但阻止了回归原始状态,突出了蛋白质进化的历史偶然性.
科学领域:
- 进化生物学 进化生物学
- 分子生物学分子生物学
- 生物化学 生物化学
背景情况:
- 进化过程的可逆性,特别是对于蛋白质功能等复杂的特征,仍然是生物学中的一个重要问题.
- 之前关于进化逆转性的研究受限于方法上的挑战和缺乏机械的理解.
- 了解导致进化不可逆转的因素对于理解生命的历史和未来至关重要.
研究的目的:
- 用一个特定的案例研究来研究蛋白质结构和功能的进化变化的可逆性.
- 确定脊椎动物葡萄糖皮质体受体激素特异性进化不可逆性的机制基础.
- 评估历史偶然性在塑造进化轨迹中的作用.
主要方法:
- 祖先基因重建以重建过去的蛋白质形式.
- 蛋白质工程系统地改变特定突变.
- 用X射线晶体学来确定蛋白质变体的三维结构.
主要成果:
- 葡萄糖皮质体受体中新激素特异性的演变涉及五种"限制性"突变,这些突变优化了新功能.
- 这些限制性突变破坏了祖先构造所需的蛋白质结构的稳定性,使直接逆转变得不起作用.
- 仅仅逆转限制性突变并不能恢复祖先的功能,这表明一种单向的进化路径.
结论:
- 导致新的蛋白质功能的进化途径可能由于随后的优化突变而变得进化难以接近.
- 观察到的"状"表观表明,历史偶然性在蛋白质进化中起着关键作用.
- 蛋白质复杂进化变化的直接逆转不太可能,即使在祖先状态的强有力的选择性压力下也是如此.
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