Iron Catalysis at the Origin of Life
Iron Catalysis at the Origin of Life
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DOI：
10.1002/iub.1632
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发表时间：
2017-06-01
期刊：
影响因子：
4.6
通讯作者：
Lane, Nick
中科院分区：
文献类型：
--
作者：
Camprubi, Eloi;Jordan, Sean F.;Lane, Nick
铁硫蛋白是一种古老的蛋白质，它驱动着细胞中的基本过程，尤其是电子转移和二氧化碳固定。具有相同结构的铁硫矿物可能在生命起源中发挥了关键作用。然而，人们对“铁硫世界”假说褒贬不一，特别是对黄铁矿拉动的逆克雷布斯循环的可行性提出了质疑。系统发育表明，最早的细胞通过乙酰辅酶a途径驱动碳和能量代谢，该途径也充满了Fe(Ni)S蛋白。细菌和古细菌在这一途径上的深层差异掩盖了祖先的状态。如果早期细胞依赖碱性热液喷口的天然质子梯度，这些差异就说得通了。如果是这样的话，乙酰辅酶a途径与活性离子泵的起源不同，祖先的二氧化碳固定可能相当于甲烷菌，后者依赖于膜结合的NiFe氢化酶，即能量转换氢化酶。它利用质子动力来还原铁氧还蛋白，从而还原二氧化碳。其机制提示pH可以调节酶活性部位的还原电位，促进H-2对CO2的难还原。这种机制可以在非生物条件下推广，因此，半导体Fe(Ni) S屏障之间的陡峭pH差异不仅驱动二氧化碳固定到C1和C2有机物（如CO， CH3SH和CH3COSH）的第一步，而且还驱动一系列类似的羰基化和氢化反应，形成长链羧酸，如丙酮酸，草酰乙酸和a-酮戊二酸，就像在甲烷菌中发现的不完全逆克雷布斯循环一样。我们认为，通过直接再生乙酰辅酶a，关闭了一个完整的反向克雷布斯循环，取代了许多现代基团的乙酰辅酶a途径。后来对乙酰辅酶A和ATP的依赖消除了质子动力驱动逆克雷布斯循环的大部分步骤的需要。VC 2017作者ubmb生活由Wiley期刊公司出版。
Iron-sulphur proteins are ancient and drive fundamental processes in cells, notably electron transfer and CO2 fixation. Iron-sulphur minerals with equivalent structures could have played a key role in the origin of life. However, the 'iron-sulphur world' hypothesis has had a mixed reception, with questions raised especially about the feasibility of a pyrites-pulled reverse Krebs cycle. Phylogenetics suggests that the earliest cells drove carbon and energy metabolism via the acetyl CoA pathway, which is also replete in Fe(Ni)S proteins. Deep differences between bacteria and archaea in this pathway obscure the ancestral state. These differences make sense if early cells depended on natural proton gradients in alkaline hydrothermal vents. If so, the acetyl CoA pathway diverged with the origins of active ion pumping, and ancestral CO2 fixation might have been equivalent to methanogens, which depend on a membrane-bound NiFe hydrogenase, energy converting hydrogenase. This uses the proton-motive force to reduce ferredoxin, thence CO2. The mechanism suggests that pH could modulate reduction potential at the active site of the enzyme, facilitating the difficult reduction of CO2 by H-2. This mechanism could be generalised under abiotic conditions so that steep pH differences across semi-conducting Fe(Ni) S barriers drives not just the first steps of CO2 fixation to C1 and C2 organics such as CO, CH3SH and CH3COSH, but a series of similar carbonylation and hydrogenation reactions to form longer chain carboxylic acids such as pyruvate, oxaloacetate and a-ketoglutarate, as in the incomplete reverse Krebs cycle found in methanogens. We suggest that the closure of a complete reverse Krebs cycle, by regenerating acetyl CoA directly, displaced the acetyl CoA pathway from many modern groups. A later reliance on acetyl CoA and ATP eliminated the need for the proton-motive force to drive most steps of the reverse Krebs cycle. VC 2017 The Authors IUBMB Life published by Wiley Periodicals, Inc.