Intense neutral drifts yield robust and evolvable consensus proteins
Intense neutral drifts yield robust and evolvable consensus proteins
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DOI：
10.1016/j.jmb.2008.04.024
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发表时间：
2008-06-20
影响因子：
5.6
通讯作者：
Tawfik, Dan S.
中科院分区：
文献类型：
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作者：
Bershtein, Shimon;Goldin, Korina;Tawfik, Dan S.
当一个低突变率的天然蛋白质在高突变负荷下发生中性漂移时，会发生什么变化，从而产生遗传多样性（多态性）基因集合，这些基因集合都保持了蛋白质的原始功能和结构？为了解决这个问题，我们对大量TEM-1 β-内酰胺酶进行了长时间的中性漂移，应用高突变率和纯化选择来维持TEM-1现有的青霉素酶活性。清除有害的突变和丰富的有益的保持这些合奏的序列更接近TEM-1的家庭共识和推断的祖先。特别是，增加TEM-1的动力学和热力学稳定性的回到共识/祖先突变被富集。这些基因充当了全局抑制因子，使它们能够容忍广泛的有害突变，从而进一步增加了漂流种群的遗传多样性。由于存在许多携带全局抑制因子的基因变异，在这些集合中出现新功能（头孢噻肟降解）的概率也大幅增加。我们的研究结果表明，在高突变负荷下产生的大型多态性中性系综的独特功能，并提示推测今天的蛋白质的祖先可能已经在高突变负荷下进化。研究结果还表明，可预测的回到共识/祖先的变化可以在实验室中使用，以产生高度多样性和可进化的基因库。(C)2008爱思唯尔有限公司保留所有权利。
What changes occur when a natural protein that had been under low mutation rates is subjected to a neutral drift at high mutational loads, thus generating genetically diverse (polymorphic) gene ensembles that all maintain the protein's original function and structure? To address this question we subjected large populations of TEM-1 beta-lactamase to a prolonged neutral drift, applying high mutation rates and purifying selection to maintain TEM-1's existing penicillinase activity. Purging of deleterious mutations and enrichment of beneficial ones maintained the sequence of these ensembles closer to TEM-1's family consensus and inferred ancestor. In particular, back-to-consensus/ancestor mutations that increase TEM-1's kinetic and thermodynamic stability were enriched. These acted as global suppressors and enabled the tolerance of a broad range of deleterious mutations, thus further increasing the genetic diversity of the drifting populations. The probability of a new function emerging (cefotaxime degradation) was also substantially increased in these ensembles owing to the presence of many gene variants carrying the global suppressors. Our findings indicate the unique features of large, polymorphic neutral ensembles generated under high mutational loads and prompt the speculation that the progenitors of today's proteins may have evolved under high mutational loads. The results also suggest that predictable back-to-consensus/ancestor changes can be used in the laboratory to generate highly diverse and evolvable gene libraries. (C) 2008 Elsevier Ltd. All rights reserved.