Université de Toulouse, F-31077 Toulouse, France.
Proc Natl Acad Sci U S A. 2011 Jan 25;108(4):1278-83. doi: 10.1073/pnas.1010431108. Epub 2011 Jan 4.
Bacterial metabolism is characterized by a remarkable capacity to rapidly adapt to environmental changes. We restructured the central metabolic network in Escherichia coli to force a higher production of NADPH, and then grew this strain in conditions favoring adaptive evolution. A six-fold increase in growth capacity was attained that could be attributed in multiple clones, after whole genome mutation mapping, to a specific single mutation. Each clone had an evolved NuoF*(E183A) enzyme in the respiratory complex I that can now oxidize both NADH and NADPH. When a further strain was constructed with an even higher degree of NADPH stress such that growth was impossible on glucose mineral medium, a solid-state screening for mutations restoring growth, led to two different types of NuoF mutations in strains having recovered growth capacity. In addition to the previously seen E183A mutation other clones showed a E183G mutation, both having NADH and NADPH oxidizing ability. These results demonstrate the unique solution used by E. coli to overcome the NADPH stress problem. This solution creates a new function for NADPH that is no longer restricted to anabolic synthesis reactions but can now be also used to directly produce catabolic energy.
细菌代谢的特点是能够迅速适应环境变化。我们重构了大肠杆菌的中心代谢网络，以强制提高 NADPH 的产量，然后在有利于适应性进化的条件下培养这种菌株。经过全基因组突变映射，在多个克隆中实现了六倍的生长能力的增加，这可以归因于一个特定的单一突变。每个克隆的呼吸复合物 I 中的进化 NuoF*（E183A）酶现在可以氧化 NADH 和 NADPH。当进一步构建了一种具有更高 NADPH 胁迫程度的菌株，以至于在葡萄糖矿物质培养基上无法生长时，通过固态筛选恢复生长的突变，导致在恢复生长能力的菌株中出现两种不同类型的 NuoF 突变。除了以前看到的 E183A 突变外，其他克隆还显示出 E183G 突变，两者都具有氧化 NADH 和 NADPH 的能力。这些结果表明大肠杆菌用于克服 NADPH 应激问题的独特解决方案。该解决方案为 NADPH 创造了一种新的功能，不再仅限于合成代谢反应，现在还可以用于直接产生分解代谢能量。
