Elferink M G, de Wit J G, Demel R, Driessen A J, Konings W N
Department of Microbiology, University of Groningen, Haren, The Netherlands.
J Biol Chem. 1992 Jan 15;267(2):1375-81.
Membranes of Sulfolobus acidocaldarius, an extreme thermophilic archaebacterium, are composed of unusual bipolar lipids. They consist of macrocyclic tetraethers with two polar heads linked by two hydrophobic C40 phytanyl chains which are thought to be arranged as a monolayer in the cytoplasmic membrane. Fractionation of a total lipid-extract from S. acidocaldarius yielded a lipid fraction which forms closed and stable unilamellar liposomes in aqueous media. Beef heart cytochrome c-oxidase could be functionally reconstituted in these liposomes. In the presence of reduced cytochrome c, a protonmotive force (delta p) across the liposomal membrane was generated of up to -92 mV. Upon fusion of these proteoliposomes with membrane vesicles of Lactococcus lactis, the delta p generated by cytochrome c-oxidase activity was capable to drive uphill transport of leucine. Electron microscopic analysis indicated that the tetraether lipids form a single monolayer liposome. The results demonstrate that tetraether lipids of archaebacteria can form a suitable matrix for the function of exogenous membrane proteins originating from a regular lipid bilayer.
嗜酸热硫化叶菌是一种嗜热古细菌，其细胞膜由不同寻常的双极脂质组成。它们由大环四醚构成，两个极性头部通过两条疏水的C40植烷链相连，这两条链在细胞质膜中被认为是以单层形式排列的。从嗜酸热硫化叶菌中提取的总脂质经分级分离后得到一种脂质组分，该组分在水性介质中形成封闭且稳定的单层脂质体。牛肉心细胞色素c氧化酶能够在这些脂质体中进行功能重建。在还原型细胞色素c存在的情况下，跨脂质体膜产生的质子动力势（Δp）高达 -92 mV。当这些蛋白脂质体与乳酸乳球菌的膜囊泡融合时，细胞色素c氧化酶活性产生的Δp能够驱动亮氨酸的上坡运输。电子显微镜分析表明，四醚脂质形成了单层脂质体。结果表明，古细菌的四醚脂质可以为源自常规脂质双层的外源膜蛋白的功能形成合适的基质。
