ConspectusCentraltothequestofunderstandingtheemergenceoflifeistouncovertheroleofmetals,特别是铁,塑造益生元化学。熨斗,作为地球上最丰富的过渡金属,在早期生化过程中起着关键作用,并且仍然是现代生物学不可或缺的。这里,我们讨论了我们最近对探索益生元与铁配合物的合理性的贡献,包括血红素和铁硫簇,在对原始细胞有益的介导化学中。实验室实验和光谱发现表明了合理的途径,通常由紫外线促进,用于合成血红素和铁硫簇。一旦形成,血红素显示催化,与两亲物复合时的过氧化物酶样活性。这种活动可能在两个方面是有益的。首先,血红素可以催化去除可能对原始细胞具有降解作用的分子(H2O2)。第二,血红素可以通过将H2O2的还原与有机底物的氧化相结合来帮助合成生命的组成部分。两亲物的必要性,以避免血红素的非活性复合物的形成是告诉,因为现代电子传输链具有嵌入脂质膜内的血红素。相反,益生元铁硫肽尚未被报道分配到脂质膜中,也没有发现简单的铁硫肽能够参与有机分子的合成。相反,铁硫肽跨越与血红素的还原电位互补的宽范围的还原电位。铁硫肽的还原电位可以通过形成的铁硫簇的类型来调节,例如,[2Fe-2S]与[4Fe-4S],或通过配体取代金属中心。由于铁离子之间的随机相遇容易形成铁硫簇,氢硫化物,和具有硫醇盐的有机小分子,包括肽,可溶性铁硫簇的可能性似乎很高。仍然难以确定的是,铁硫肽是否参与了早期的益生元化学,或者在原始细胞膜进化后被招募,该细胞膜与利用电子转移作为质子梯度储存能量相容。这个问题在某种程度上反映了破译整个新陈代谢起源的困难。类似于现存代谢的某些方面的化学必须在益生元地球上发生,但是关于如何以及何时利用这种化学物质来支持(原始)细胞的线索很少。最终,揭示血红素和铁硫簇在益生元化学中的作用有望加深我们对地球生命起源的理解,并有助于在宇宙中其他地方寻找生命。
ConspectusCentral to the quest of understanding the emergence of life is to uncover the role of metals, particularly iron, in shaping prebiotic chemistry. Iron, as the most abundant of the accessible transition metals on the prebiotic Earth, played a pivotal role in early biochemical processes and continues to be indispensable to modern biology. Here, we discuss our recent contributions to probing the plausibility of prebiotic complexes with iron, including heme and iron-sulfur clusters, in mediating chemistry beneficial to a protocell. Laboratory experiments and spectroscopic findings suggest plausible pathways, often facilitated by UV light, for the synthesis of heme and iron-sulfur clusters. Once formed, heme displays catalytic, peroxidase-like activity when complexed with amphiphiles. This activity could have been beneficial in two ways. First, heme could have catalytically removed a molecule (H2O2) that could have had degradative effects on a protocell. Second, heme could have helped in the synthesis of the building blocks of life by coupling the reduction of H2O2 with the oxidation of organic substrates. The necessity of amphiphiles to avoid the formation of inactive complexes of heme is telling, as the modern-day electron transport chain possesses heme embedded within a lipid membrane. Conversely, prebiotic iron-sulfur peptides have yet to be reported to partition into lipid membranes, nor have simple iron-sulfur peptides been found to be capable of participating in the synthesis of organic molecules. Instead, iron-sulfur peptides span a wide range of reduction potentials complementary to the reduction potentials of hemes. The reduction potential of iron-sulfur peptides can be tuned by the type of iron-sulfur cluster formed, e.g., [2Fe-2S] versus [4Fe-4S], or by the substitution of ligands to the metal center. Since iron-sulfur clusters easily form upon stochastic encounters between iron ions, hydrosulfide, and small organic molecules possessing a thiolate, including peptides, the likelihood of soluble iron-sulfur clusters seems to be high. What remains challenging to determine is if iron-sulfur peptides participated in early prebiotic chemistry or were recruited later when protocellular membranes evolved that were compatible with the exploitation of electron transfer for the storage of energy as a proton gradient. This problem mirrors in some ways the difficulty in deciphering the origins of metabolism as a whole. Chemistry that resembles some facets of extant metabolism must have transpired on the prebiotic Earth, but there are few clues as to how and when such chemistry was harnessed to support a (proto)cell. Ultimately, unraveling the roles of hemes and iron-sulfur clusters in prebiotic chemistry promises to deepen our understanding of the origins of life on Earth and aids the search for life elsewhere in the universe.