Heberle J, Riesle J, Thiedemann G, Oesterhelt D, Dencher N A
Hahn-Meitner-Institut, Berlin, Germany.
Nature. 1994 Aug 4;370(6488):379-82. doi: 10.1038/370379a0.
Since the proposal of the chemiosmotic theory there has been a continuing debate about how protons that have been pumped across membranes reach another membrane protein that utilizes the established pH gradient. Evidence has been gathered in favour of a 'delocalized' theory, in which the pumped protons equilibrate with the aqueous bulk phase before being consumed, and a 'localized' one, in which protons move exclusively along the membrane surface. We report here that after proton release by an integral membrane protein, long-range proton transfer along the membrane surface is faster than proton exchange with the bulk water phase. The rate of lateral proton diffusion can be calculated by considering the buffer capacity of the membrane surface. Our results suggest that protons can efficiently diffuse along the membrane surface between a source and a sink (for example H(+)-ATP synthase) without dissipation losses into the aqueous bulk.
自从化学渗透理论提出以来，关于泵过膜的质子如何到达另一种利用已建立的pH梯度的膜蛋白一直存在持续的争论。已经收集到的证据支持一种“离域化”理论，即泵出的质子在被消耗之前先与水相主体达到平衡；以及一种“局域化”理论，即质子仅沿着膜表面移动。我们在此报告，在整合膜蛋白释放质子后，沿膜表面的长程质子转移比与水相主体的质子交换更快。可以通过考虑膜表面的缓冲能力来计算横向质子扩散速率。我们的结果表明，质子能够在源和汇（例如H⁺-ATP合酶）之间沿着膜表面高效扩散，而不会耗散到水相主体中。
