Small changes in enzyme function can lead to surprisingly large fitness effects during adaptive evolution of antibiotic resistance.
Small changes in enzyme function can lead to surprisingly large fitness effects during adaptive evolution of antibiotic resistance.
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在抗生素耐药性的适应性进化过程中，酶功能的微小变化可能会导致惊人的巨大适应性效应。
DOI：
10.1073/pnas.1209335110
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发表时间：
2012
影响因子：
11.1
通讯作者：
Shamoo,Yousif
中科院分区：
文献类型：
--
作者：
Walkiewicz,Katarzyna;BenitezCardenas,AndresS;Sun,Christine;Bacorn,Colin;Saxer,Gerda;Shamoo,Yousif
原则上，如果已知特定蛋白质功能的所有相关物理化学变体并将其整合到适当的生理模型中，则可以在很大程度上预测进化结果。我们已经通过产生四环素抗性蛋白TetX2的变体家族来测试这一原理，并确定了与生物体适应性最相关的理化性质。令人惊讶的是，Km（MCN）的微小变化（不到两倍）足以在临床相关药物浓度下产生高度成功的适应性突变体。然后，我们建立了一个定量模型，直接相关的突变酶的体外理化性质的细菌携带一个单一的染色体拷贝的thetet（X2）变体在很宽的米诺环素（MCN）浓度的生长速率。重要的是，该模型允许直接从细胞生长速率以及TetX2的理化适应性景观预测酶特性。使用实验进化和深度测序来监测10个独立进化群体中7个最具生化效率的TetX2突变体的等位基因频率，我们发现该模型正确预测了两个最有益的变异体stet（X2）T280 A和tet（X2）N371 I的成功。最有效的变体TetX2T280A的结构与MCN在2.7 μ m分辨率下复合，表明对酶动力学有间接影响。总的来说，这些发现支持了蛋白质进化中容易获得的小步骤的重要作用，这些小步骤反过来可以大大增加生物体在自然选择中的适应性。
In principle, evolutionary outcomes could be largely predicted if all of the relevant physicochemical variants of a particular protein function under selection were known and integrated into an appropriate physiological model. We have tested this principle by generating a family of variants of the tetracycline resistance protein TetX2 and identified the physicochemical properties most correlated with organismal fitness. Surprisingly, small changes in theKm(MCN), less than twofold, were sufficient to produce highly successful adaptive mutants over clinically relevant drug concentrations. We then built a quantitative model directly relating the in vitro physicochemical properties of the mutant enzymes to the growth rates of bacteria carrying a single chromosomal copy of thetet(X2)variants over a wide range of minocycline (MCN) concentrations. Importantly, this model allows the prediction of enzymatic properties directly from cellular growth rates as well as the physicochemical-fitness landscape of TetX2. Using experimental evolution and deep sequencing to monitor the allelic frequencies of the seven most biochemically efficient TetX2 mutants in 10 independently evolving populations, we showed that the model correctly predicted the success of the two most beneficial variantstet(X2)T280Aandtet(X2)N371I. The structure of the most efficient variant, TetX2T280A, in complex with MCN at 2.7 Å resolution suggests an indirect effect on enzyme kinetics. Taken together, these findings support an important role for readily accessible small steps in protein evolution that can, in turn, greatly increase the fitness of an organism during natural selection.