Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119991, Russia.
Proc Natl Acad Sci U S A. 2011 Oct 18;108(42):17320-4. doi: 10.1073/pnas.1108217108. Epub 2011 Oct 10.
Escherichia coli is known to couple aerobic respiratory catabolism to ATP synthesis by virtue of the primary generators of the proton motive force-NADH dehydrogenase I, cytochrome bo(3), and cytochrome bd-I. An E. coli mutant deficient in NADH dehydrogenase I, bo(3) and bd-I can, nevertheless, grow aerobically on nonfermentable substrates, although its sole terminal oxidase cytochrome bd-II has been reported to be nonelectrogenic. In the current work, the ability of cytochrome bd-II to generate a proton motive force is reexamined. Absorption and fluorescence spectroscopy and oxygen pulse methods show that in the steady-state, cytochrome bd-II does generate a proton motive force with a H(+)/e(-) ratio of 0.94 ± 0.18. This proton motive force is sufficient to drive ATP synthesis and transport of nutrients. Microsecond time-resolved, single-turnover electrometry shows that the molecular mechanism of generating the proton motive force is identical to that in cytochrome bd-I. The ability to induce cytochrome bd-II biosynthesis allows E. coli to remain energetically competent under a variety of environmental conditions.
大肠杆菌（Escherichia coli）已知能够通过质子动力势的主要产生器——NADH 脱氢酶 I、细胞色素 bo(3)和细胞色素 bd-I 将需氧呼吸分解代谢与 ATP 合成偶联。尽管大肠杆菌突变体缺乏 NADH 脱氢酶 I、bo(3)和 bd-I，但仍能在非发酵底物上进行需氧生长，尽管据报道其唯一的末端氧化酶细胞色素 bd-II 是非发电的。在当前的工作中，重新检查了细胞色素 bd-II 产生质子动力势的能力。吸收和荧光光谱以及氧脉冲方法表明，在稳态下，细胞色素 bd-II 确实会产生质子动力势，其 H(+)/e(-) 比为 0.94 ± 0.18。该质子动力势足以驱动 ATP 合成和营养物质的运输。微秒时间分辨、单周转电子计量表明，产生质子动力势的分子机制与细胞色素 bd-I 相同。诱导细胞色素 bd-II 生物合成的能力使大肠杆菌能够在各种环境条件下保持能量适应性。
