Template-directed synthesis of a genetic polymer in a model protocell
Template-directed synthesis of a genetic polymer in a model protocell
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DOI：
10.1038/nature07018
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发表时间：
2008-07-03
期刊：
影响因子：
64.8
通讯作者：
Szostak, Jack W.
中科院分区：
文献类型：
--
作者：
Mansy, Sheref S.;Schrum, Jason P.;Szostak, Jack W.
当代的磷脂基细胞膜是吸收极性和带电分子的强大屏障，从金属离子到复杂的营养物质。因此，现代细胞需要复杂的蛋白质通道和泵来介导分子与环境的交换。细胞膜的强大屏障功能使得理解细胞生命的起源变得困难，并且被认为排除了原始细胞的异养生活方式。虽然核苷酸可以通过在凝胶-液体转变温度下形成的缺陷穿过二肉豆蔻酰磷脂酰胆碱膜（1，2），但磷脂膜缺乏膜生长所需的动力学性质.脂肪酸及其相应的醇和甘油单酯是原始细胞膜组分的有吸引力的候选物，因为它们是简单的两亲物，形成双层膜囊泡（3-5），其保留包封的寡核苷酸（3，6）并且能够生长和分裂（7-9）。在这里，我们表明，这样的膜允许带电的分子，如核苷酸的通道，使激活的核苷酸添加到外部的模型原始细胞自发地穿过膜，并在原始细胞内部的有效模板复制的一部分。前生物学上合理的膜的渗透性表明，原始的原始细胞可以在没有任何大分子运输机制的情况下从环境中获得复杂的营养物质;也就是说，它们可能是专性异养生物。
Contemporary phospholipid- based cell membranes are formidable barriers to the uptake of polar and charged molecules ranging from metal ions to complex nutrients. Modern cells therefore require sophisticated protein channels and pumps to mediate the exchange of molecules with their environment. The strong barrier function of membranes has made it difficult to understand the origin of cellular life and has been thought to preclude a heterotrophic lifestyle for primitive cells. Although nucleotides can cross dimyristoyl phosphatidylcholine membranes through defects formed at the gel- to- liquid transition temperature(1,2), phospholipid membranes lack the dynamic properties required for membrane growth. Fatty acids and their corresponding alcohols and glycerol monoesters are attractive candidates for the components of protocell membranes because they are simple amphiphiles that form bilayer membrane vesicles(3-5) that retain encapsulated oligonucleotides(3,6) and are capable of growth and division(7-9). Here we show that such membranes allow the passage of charged molecules such as nucleotides, so that activated nucleotides added to the outside of a model protocell spontaneously cross the membrane and take part in efficient template copying in the protocell interior. The permeability properties of prebiotically plausible membranes suggest that primitive protocells could have acquired complex nutrients from their environment in the absence of any macromolecular transport machinery; that is, they could have been obligate heterotrophs.