Convergent evolution of unusual complex I homologs with increased proton pumping capacity: energetic and ecological implications
Convergent evolution of unusual complex I homologs with increased proton pumping capacity: energetic and ecological implications
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DOI：
10.1038/s41396-018-0210-1
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发表时间：
2018-11-01
期刊：
影响因子：
11
通讯作者：
Orphan, Victoria J.
中科院分区：
文献类型：
--
作者：
Chadwick, Grayson L.;Hemp, James;Orphan, Victoria J.
呼吸复合物I是一个大家族的同源酶的一部分，进行可溶性细胞质电子载体和膜结合电子载体之间的电子转移。这些复合物是重要的生物能酶，其作为进入各种微生物代谢的电子传递链的入口点，并且电子传递与质子易位耦合。这种酶的核心复合物由11个蛋白质亚基组成，其中有三个主要的质子泵亚基。在这里，我们记录了在来自不同培养细菌、鸟枪宏基因组学和环境来源的古细菌fosmids的基因组序列中发现的大量修饰的复合体I基因盒，所有这些都编码第四个质子泵亚基。这种额外的亚基结合到功能性蛋白质复合物中是由蛋白质复合物长度上的两亲性螺旋中的大氨基酸插入支持的。系统发育分析表明，这些修改后的复合物似乎已经出现了独立的收敛分子进化的一个显着的情况下多次。从一个充满活力的角度来看，我们假设，这种修改的典型的复合物I架构允许每个反应周期的第五个质子的易位，这种修改后的复合物的生理效用进行了讨论。
Respiratory complex I is part of a large family of homologous enzymes that carry out the transfer of electrons between soluble cytoplasmic electron carriers and membrane-bound electron carriers. These complexes are vital bioenergetic enzymes that serve as the entry points into electron transport chains for a wide variety of microbial metabolisms, and electron transfer is coupled to proton translocation. The core complex of this enzyme is made up of 11 protein subunits, with three major proton pumping subunits. Here, we document a large number of modified complex I gene cassettes found in genome sequences from diverse cultured bacteria, shotgun metagenomics, and environmentally derived archaeal fosmids all of which encode a fourth proton pumping subunit. The incorporation of this extra subunit into a functional protein complex is supported by large amino acid insertions in the amphipathic helix that runs the length of the protein complex. Phylogenetic analyses reveal that these modified complexes appear to have arisen independently multiple times in a remarkable case of convergent molecular evolution. From an energetic perspective, we hypothesize that this modification on the canonical complex I architecture allows for the translocation of a fifth proton per reaction cycle-the physiological utility of this modified complex is discussed.