Mitochondrial complex I is the main site for electron transfer to the respiratory chain and generates much of the proton gradient across the inner mitochondrial membrane. It is composed of two arms, which form a conserved L-shape. We report the structures of the intact, 47-subunit mitochondrial complex I from Arabidopsis thaliana and from the green alga Polytomella sp. at 3.2 and 3.3 Angstrom resolution. In both, a heterotrimeric gamma-carbonic anhydrase domain is attached to the membrane arm on the matrix side. Two states are resolved in A. thaliana complex I, with different angles between the two arms and different conformations of the ND1 loop near the quinol binding site. The angle appears to depend on a bridge domain, which links the peripheral arm to the membrane arm and includes an unusual ferredoxin. We suggest that the bridge domain regulates complex I activity.

中文翻译：

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铁氧还蛋白桥连接植物线粒体复合体I的两个臂

线粒体复合体I是电子转移到呼吸链的主要部位，并在整个线粒体内膜上产生许多质子梯度。它由两个臂组成，形成一个保守的L形。我们报告从拟南芥和绿色藻类Polytomella sp完整，47亚基线粒体复合体I的结构。在3.2和3.3埃分辨率下。在这两者中，异三聚体γ-碳酸酐酶结构域在基质侧附接到膜臂。在拟南芥复合体I中解析出两个状态，两个臂之间的角度不同，并且喹诺酮结合位点附近的ND1环的构型不同。角度似乎取决于桥结构域，桥结构域将外围臂连接到膜臂，并包含一种异常的铁氧还蛋白。