Uncovering the [2Fe2S] domain movement in cytochrome bc1 and its implications for energy conversion
Uncovering the [2Fe2S] domain movement in cytochrome bc1 and its implications for energy conversion
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DOI：
10.1073/pnas.97.9.4567
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发表时间：
2000-04-25
影响因子：
11.1
通讯作者：
Daldal, F
中科院分区：
文献类型：
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作者：
Darrouzet, E;Valkova-Valchanova, M;Daldal, F
在呼吸和光合作用的关键电子转移蛋白泛氢苯二酚：细胞色素(Cyt)c氧化还原酶(Cyt BC(1))的晶体中，其Fe-S亚基的外源[2Fe2S]簇结构域呈多种构象，表明它可能在催化过程中移动。在这里，使用在该亚单位的铰链区具有修饰的胶囊红杆菌突变体，我们能够动态地揭示这一运动。因此。BC(1)复合体(可能是叶绿体中的同源b(6)f复合体)利用[2Fe2S]簇结构域作为一种装置，将电子从泛氢对苯二酚传递到cytc(1)(或cytf)。我们证明这种结构域的移动是细胞色素BC(1)功能所必需的，因为含有不移动的Fe-S亚基的突变酶没有催化活性，而运动较慢的突变酶的活性较低。这项运动显然是用自然频率设计的，足够慢，以确保有效的Q(0)位电荷分离，但又足够快，不受速率限制。这些发现为蛋白质中的大规模结构域运动增加了前所未有的复合体内电子穿梭的功能，并很可能成为CytBC(1)抗生素的靶标。
In crystals of the key respiratory and photosynthetic electron transfer protein called ubihydroquinone:cytochrome (cyt) c oxidoreductase or cyt bc(1), the extrinsic [2Fe2S] cluster domain of its Fe-S subunit assumes several conformations, suggesting that it may move during catalysis. Herein, using Rhodobacter capsulatus mutants that have modifications in the hinge region of this subunit, we were able to reveal this motion kinetically. Thus. the bc(1) complex (and possibly the homologous b(6)f complex in chloroplasts) employs the [2Fe2S] cluster domain as a device to shuttle electrons from ubihydroquinone to cyt c(1) (or cyt f). We demonstrate that this domain movement is essential for cyt bc(1) function, because a mutant enzyme with a nonmoving Fe-S subunit has no catalytic activity, and one with a slower movement has lower activity. This motion is apparently designed with a natural frequency slow enough to assure productive Q(0) site charge separation but fast enough not to be rate limiting. These findings add the unprecedented function of intracomplex electron shuttling to large-scale domain motions in proteins and may well provide a target for cyt bc(1) antibiotics.