Role of Subunit NuoL for Proton Translocation by Respiratory Complex I
Role of Subunit NuoL for Proton Translocation by Respiratory Complex I
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DOI：
10.1021/bi200264q
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发表时间：
2011-04-26
期刊：
影响因子：
2.9
通讯作者：
Friedrich, Thorsten
中科院分区：
文献类型：
--
作者：
Steimle, Stefan;Bajzath, Csaba;Friedrich, Thorsten
NADH：泛醌氧化还原酶，呼吸复合物I，将电子从NADH转移到泛醌与质子跨膜易位偶联。该复合物由催化电子转移反应的外周臂和参与质子移位的膜臂组成。最近公布的X-射线结构的复杂揭示了一个独特的110埃的“水平”螺旋排列的膜arm. On这一发现的基础上，有人提出，通过氧化还原反应释放的能量被传递到膜臂通过构象变化的水平螺旋。螺旋对应于最远端亚基NuoL的C末端部分。为了研究其在质子转运中的作用，我们表征了缺乏NuoL或部分C-末端结构域的复合物I变体的电子转移和质子转运活性。我们的数据表明Delta NuoL变体的H+/2 e（-）化学计量比为2，表明质子易位的化学计量比不同，如从结构数据中提出的。此外，相同的H+/e（-）化学计量得到的变体缺乏C-末端跨膜螺旋的NuoL，表明其在能量传递中的作用。
The NADH:ubiquinone oxidoreductase, respiratory complex I, couples the transfer of electrons from NADH to ubiquinone with a translocation of protons across the membrane. The complex consists of a peripheral arm catalyzing the electron transfer reaction and a membrane arm involved in proton translocation. The recently published X-ray structures of the complex revealed the presence of a unique 110 angstrom "horizontal" helix aligning the membrane arm. On the basis of this finding, it was proposed that the energy released by the redox reaction is transmitted to the membrane arm via a conformational change in the horizontal helix. The helix corresponds to the C-terminal part of the most distal subunit NuoL. To investigate its role in proton translocation, we characterized the electron transfer and proton translocation activity of complex I variants lacking either NuoL or parts of the C-terminal domain. Our data suggest that the H+/2e(-) stoichiometry of the Delta NuoL variant is 2, indicating a different stoichiometry for proton translocation as proposed from structural data. In addition, the same H+/e(-) stoichiometry is obtained with the variant lacking the C-terminal transmembraneous helix of NuoL, indicating its role in energy transmission.