Elimination of Canonical Amino Acid from Escherichia coli by Experimental Evolution

在所有关于遗传密码进化的理论中，氨基酸的数量都被假设是逐渐增加的，从几个增加到现在构成活细胞中蛋白质的20个。这项研究的目的是重建一种可能的进化中间体，在这种中间体中，一个活的有机体含有19个而不是20个氨基酸。这一目标将深入了解蛋白质结构如何适应突变，并在设计和选择适应不同化学成分的生物体方面开辟可能性。根据最近实验的令人鼓舞的结果，这一目标将通过将种群置于失去特定氨基酸的选择性压力下来实现。在大肠杆菌中用缬氨酸代替异亮氨酸和用丝氨酸代替苏氨酸设计了两种不同的策略。这些策略结合了利用经典菌株结构的选择策略和使用允许长期实验的连续培养装置。

In all the theories of the evolution of the genetic code, the number of amino acids is hypothesized to have gradually increased from a few to the twenty that now constitute the building-blocks of proteins in living cells. The objective of this research is to recreate a possible evolutionary intermediate in which a living organism contains 19 and not 20 amino acids. This objective would give insight into how protein structures adapt to mutation and open possibilities in terms of designing and selecting organisms adapted to a different chemical composition. Based on encouraging results from recent experiments, this objective will be accomplished by placing a population under selective pressure for the loss of a given amino acid. Two different strategies have been designed to replace isoleucine by valine and threonine by serine in Escherichia coli. These strategies combine selection strategies that exploit classical strain constructions with the use of a continuous culture apparatus that allows long-term experiments.