Squalane is in the midplane of the lipid bilayer: implications for its function as a proton permeability barrier
Squalane is in the midplane of the lipid bilayer: implications for its function as a proton permeability barrier
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DOI：
10.1016/s0005-2728(02)00346-8
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发表时间：
2002-12-02
影响因子：
4.3
通讯作者：
Haines, TH
中科院分区：
文献类型：
--
作者：
Hauss, T;Dante, S;Haines, TH
最近提出的质子跨生物膜泄漏模型[j]。脂质Res. 40(2001) 299]表明，特别是在脂质双分子层中心的碳氢化合物抑制质子泄漏。由于细胞膜维持质子电化学梯度作为主要的能量换能器，质子泄漏消耗细胞能量无效。双分子层中的碳氢化合物在维持这种梯度的膜中广泛存在。亲碱菌的独特之处在于它们的膜中含有高达40摩尔%的异戊二烯，包括10-11摩尔%的角鲨烯[J]。细菌学杂志。[8]。角鲨烯是一种没有极性基团的聚异戊二烯烃。在脂质双分子层中定位碳氢化合物并非易事。包括荧光光谱、电子自旋共振、核磁共振以及x射线和中子衍射在内的无数物理方法都被用来探索这个问题，取得了不同程度的成功，但结果往往相互矛盾。为了寻找角鲨烯在膜或脂质双层中定位的明确证据，我们采用了中子衍射。我们将10 mol%的角鲨烯（角鲨烯的一种等构类似物）过氘化或质子化，加入掺杂了二油酰磷脂酰胆碱（DOPC）和二油酰磷脂酰甘油（DOPG）的堆叠双层中，以模拟天然膜上的负电荷。中子衍射数据清楚地表明，角鲨烷主要位于双层中心，平行于膜的平面。(C) 2002 Elsevier Science B.V.版权所有
A recently proposed model for proton leakage across biological membranes [Prog. Lipid Res. 40 (2001) 299] suggested that hydrocarbons specifically in the center of the lipid bilayer inhibit proton leaks. Since cellular membranes maintain a proton electrochemical gradient as a principal energy transducer, proton leakage unproductively consumes cellular energy. Hydrocarbons in the bilayer are widespread in membranes that sustain such gradients. The alkaliphiles are unique in that they contain up to 40 mol% isoprenes in their membranes including 10-11 mol% squalene [J. Bacteriol. 168 (1986) 334]. Squalene is a polyisoprene hydrocarbon without polar groups. Localizing hydrocarbons in lipid bilayers has not been trivial. A myriad of physical methods including fluorescence spectroscopy, electron-spin resonance, nuclear magnetic resonance as well as X-ray and neutron diffraction have been used to explore this question with various degrees of success and often contradictory results. Seeking unambiguous evidence for the localization of squalene in membranes or lipid bilayers, we employed neutron diffraction. We incorporated 10 mol% perdeuterated or protonated squalane, an isosteric analogue of squalene, into stacked bilayers of dioleoyl phosphatidyl choline (DOPC) doped with dioleoyl phosphatidyl glycerol (DOPG) to simulate the negative charges found on natural membranes. The neutron diffraction data clearly show that the squalane lies predominantly in the bilayer center, parallel to the plane of the membrane. (C) 2002 Elsevier Science B.V. All rights reserved.