Complex I是呼吸链的第一种酶，它通过将NADH和苯醌之间的电子转移同质子转位耦合起来，而在线粒体中的细胞能量生产中扮演一个中心角色。这个巨大的复合物是呼吸链的最后环节，其机制和完整结构过去并不为人们所知。
现在，来自大肠杆菌的Complex I的膜区域以及来自温泉菌（嗜热菌）的完整Complex I的结构已被确定。这些结构提供了关于耦合机制的有力线索：两个主要区域界面上发生的构形变化，会驱动一个长阿尔法螺旋发生一种活塞式运动，使附近跨膜螺旋倾斜，导致质子转位。本期封面图片所描绘的是来自嵌入在类脂双层中的温泉菌（嗜热菌）的呼吸链Complex I。每个亚单元都用不同颜色表示，亲水区域中的Fe-S簇显示为球形。背景所示为偏振光下的膜区域的晶体。(生物谷Bioon.com)
ATP的生成、储存和利用
呼 吸 链?
生物谷推荐原文出处：
Nature doi:10.1038/nature09066
The architecture of respiratory complex I
Rouslan G. Efremov 1, Rozbeh Baradaran 1 & Leonid A. Sazanov 1
1 Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0xY, UK
Complex I is the first enzyme of the respiratory chain and has a central role in cellular energy production, coupling electron transfer between NADH and quinone to proton translocation by an unknown mechanism. Dysfunction of complex I has been implicated in many human neurodegenerative diseases. We have determined the structure of its hydrophilic domain previously. Here, we report the α-helical structure of the membrane domain of complex I from Escherichia coli at 3.9?? resolution. The antiporter-like subunits NuoL/M/N each contain 14 conserved transmembrane (TM) helices. Two of them are discontinuous, as in some transporters. Unexpectedly, subunit NuoL also contains a 110-? long amphipathic α-helix, spanning almost the entire length of the domain. Furthermore, we have determined the structure of the entire complex I from Thermus thermophilus at 4.5?? resolution. The L-shaped assembly consists of the α-helical model for the membrane domain, with 63 TM helices, and the known structure of the hydrophilic domain. The architecture of the complex provides strong clues about the coupling mechanism: the conformational changes at the interface of the two main domains may drive the long amphipathic α-helix of NuoL in a piston-like motion, tilting nearby discontinuous TM helices, resulting in proton translocation.
