Microscopic rotary mechanism of ion translocation in the F0 complex of ATP synthases
Microscopic rotary mechanism of ion translocation in the F0 complex of ATP synthases
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DOI：
10.1038/nchembio.457
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发表时间：
2010-12-01
影响因子：
14.8
通讯作者：
Meier, Thomas
中科院分区：
文献类型：
--
作者：
Pogoryelov, Denys;Krah, Alexander;Meier, Thomas
F1 F0-ATP酶中C环旋转和离子移位的微观机制尚不清楚。在这里，我们提出了确凿的证据支持的概念，C-环的能力，在F-0复杂的旋转来自离子结合位点和它们的非均匀的微环境之间的相互作用。这一证据依赖于c（15）转子的三种原子结构，它们分别来自在低pH下生长的晶体、在高pH下浸泡的晶体以及在N，N '-二环己基碳二亚胺（DCCD）改性后在1.8、3.0和2.2埃下分辨的晶体。除了定量DCCD标记测定和自由能分子动力学计算之外，这些数据还展示了所谓的质子锁定状态的热力学稳定性如何通过脂膜最大化。相比之下，a-亚基-c-环界面处的亲水环境似乎解锁了结合位点构象，并促进了与周围溶液的质子交换。因此，旋转发生的c-亚基随机交替这些环境之间，电化学跨膜梯度的方向偏置。
The microscopic mechanism of coupled c-ring rotation and ion translocation in F1F0-ATP synthases is unknown. Here we present conclusive evidence supporting the notion that the ability of c-rings to rotate within the F-0 complex derives from the interplay between the ion-binding sites and their nonhomogenous microenvironment. This evidence rests on three atomic structures of the c(15) rotor from crystals grown at low pH, soaked at high pH and, after N,N'-dicyclohexylcarbodiimide (DCCD) modification, resolved at 1.8, 3.0 and 2.2 angstrom, respectively. Alongside a quantitative DCCD-labeling assay and free-energy molecular dynamics calculations, these data demonstrate how the thermodynamic stability of the so-called proton-locked state is maximized by the lipid membrane. By contrast, a hydrophilic environment at the a-subunit-c-ring interface appears to unlock the binding-site conformation and promotes proton exchange with the surrounding solution. Rotation thus occurs as c-subunits stochastically alternate between these environments, directionally biased by the electrochemical transmembrane gradient.