Natural pH Gradients in Hydrothermal Alkali Vents Were Unlikely to Have Played a Role in the Origin of Life.
Natural pH Gradients in Hydrothermal Alkali Vents Were Unlikely to Have Played a Role in the Origin of Life.
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DOI：
10.1007/s00239-016-9756-6
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发表时间：
2016-08
影响因子：
3.9
通讯作者：
Jackson JB
中科院分区：
文献类型：
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作者：
Jackson JB
有一种假设认为，在生命起源期间，海洋和热液碱喷口流出的液体之间的无机膜上存在天然的pH梯度，为驱动化学反应提供了能量，这种假设与当今生物体中化学渗透ATP合成的情况有着引人注目的相似之处。然而，在这篇综述中提出的争论表明，这样的自然pH梯度不太可能在生命的起源中发挥作用。到目前为止，还没有证据表明，在大西洋中脊附近失落之城的现代热液碱喷口中，有薄的无机膜保持着急剧的pH梯度。提出的非蛋白质形式的H+焦磷酸合成酶的模型，可以作为利用自然pH梯度能量的分子机器发挥作用，是不令人满意的。一些利用自然pH梯度驱动氧化还原反应的非蛋白质马达的假设设计是合理的，但很复杂，而且这种马达被认为不太可能在益生元时代偶然组装起来。由几百个原子组成的小分子马达将无法在相对较厚（bbb10 μm）的无机膜中发挥作用，迄今为止，无机膜一直被用作自然pH梯度假设的描述性模型。在容易出错的基因复制和翻译出现之后，化学渗透系统进化的其他假设更有可能是正确的。
The hypothesis that a natural pH gradient across inorganic membranes lying between the ocean and fluid issuing from hydrothermal alkali vents provided energy to drive chemical reactions during the origin of life has an attractive parallel with chemiosmotic ATP synthesis in present-day organisms. However, arguments raised in this review suggest that such natural pH gradients are unlikely to have played a part in life’s origin. There is as yet no evidence for thin inorganic membranes holding sharp pH gradients in modern hydrothermal alkali vents at Lost City near the Mid-Atlantic Ridge. Proposed models of non-protein forms of the H+-pyrophosphate synthase that could have functioned as a molecular machine utilizing the energy of a natural pH gradient are unsatisfactory. Some hypothetical designs of non-protein motors utilizing a natural pH gradient to drive redox reactions are plausible but complex, and such motors are deemed unlikely to have assembled by chance in prebiotic times. Small molecular motors comprising a few hundred atoms would have been unable to function in the relatively thick (>1 μm) inorganic membranes that have hitherto been used as descriptive models for the natural pH gradient hypothesis. Alternative hypotheses for the evolution of chemiosmotic systems following the emergence of error-prone gene replication and translation are more likely to be correct.