Johnson Research Foundation, Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6059, USA.
FEBS Lett. 2010 Oct 8;584(19):4131-7. doi: 10.1016/j.febslet.2010.08.039. Epub 2010 Sep 15.
Recently, Sazanov's group reported the X-ray structure of whole complex I [Nature, 465, 441 (2010)], which presented a strong clue for a "piston-like" structure as a key element in an "indirect" proton pump. We have studied the NuoL subunit which has a high sequence similarity to Na(+)/H(+) antiporters, as do the NuoM and N subunits. We constructed 27 site-directed NuoL mutants. Our data suggest that the H(+)/e(-) stoichiometry seems to have decreased from (4H(+)/2e(-)) in the wild-type to approximately (3H(+)/2e(-)) in NuoL mutants. We propose a revised hypothesis that each of the "direct" and the "indirect" proton pumps transports 2H(+) per 2e(-).
最近，Sazanov 小组报道了完整的复合物 I 的 X 射线结构[《自然》，465，441（2010）]，这为“活塞样”结构作为“间接”质子泵的关键元件提供了一个强有力的线索。我们研究了 NuoL 亚基，它与 Na(+)/H(+)反向转运蛋白具有很高的序列相似性，NuoM 和 N 亚基也是如此。我们构建了 27 个定点 NuoL 突变体。我们的数据表明，H(+)/e(-)的比例似乎从野生型的（4H(+)/2e(-)）降低到 NuoL 突变体的约（3H(+)/2e(-)）。我们提出了一个修正的假说，即“直接”和“间接”质子泵每 2e(-)转运 2H(+)。
