Max Plank Institute for Molecular Cell Biology and Genetics, 01307 Dresden, Germany.
Proc Natl Acad Sci U S A. 2012 Aug 28;109(35):14236-40. doi: 10.1073/pnas.1212141109. Epub 2012 Aug 14.
Liquid-ordered phases are one of two biochemically active membrane states, which until now were thought to be a unique consequence of the interactions between eukaryotic membrane lipids. The formation of a liquid-ordered phase depends crucially on the ordering properties of sterols. However, it is not known whether this capacity exists in organisms that lack sterols, such as bacteria. We show that diplopterol, the simplest bacterial hopanoid, has similar properties and that hopanoids are bacterial "sterol surrogates" with the ability to order saturated lipids and to form a liquid-ordered phase in model membranes. These observations suggest that the evolution of an ordered biochemically active liquid membrane could have evolved before the oxygenation of Earth's surface and the emergence of sterols.
液态有序相是两种生物化学活性膜状态之一，直到现在，人们一直认为这是真核细胞膜脂质相互作用的独特结果。液态有序相的形成取决于甾醇的有序特性。然而，目前尚不清楚在缺乏甾醇的生物体中是否存在这种能力，例如细菌。我们表明，二孢萜醇，最简单的细菌藿烷，具有相似的性质，并且藿烷是细菌“甾醇替代物”，能够对饱和脂质进行排序，并在模型膜中形成液态有序相。这些观察结果表明，在地球表面氧化和甾醇出现之前，有序的生物化学活性液态膜的进化就可能已经发生了。
