School of Chemistry and Biochemistry, and NASA Astrobiology Institute Center for Ribosomal Origins and Evolution, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Nat Chem. 2013 Jun;5(6):525-8. doi: 10.1038/nchem.1649. Epub 2013 May 19.
Mg(2+) is essential for RNA folding and catalysis. However, for the first 1.5 billion years of life on Earth RNA inhabited an anoxic Earth with abundant and benign Fe(2+). We hypothesize that Fe(2+) was an RNA cofactor when iron was abundant, and was substantially replaced by Mg(2+) during a period known as the 'great oxidation', brought on by photosynthesis. Here, we demonstrate that reversing this putative metal substitution in an anoxic environment, by removing Mg(2+) and replacing it with Fe(2+), expands the catalytic repertoire of RNA. Fe(2+) can confer on some RNAs a previously uncharacterized ability to catalyse single-electron transfer. We propose that RNA function, in analogy with protein function, can be understood fully only in the context of association with a range of possible metals. The catalysis of electron transfer, requisite for metabolic activity, may have been attenuated in RNA by photosynthesis and the rise of O2.
镁（Mg2+）是 RNA 折叠和催化所必需的。然而，在地球生命存在的最初 15 亿年里，RNA 生活在富含且良性的亚铁（Fe2+）的缺氧环境中。我们假设，在铁元素丰富的时期，Fe2+是 RNA 的辅因子，而在光合作用带来的“大氧化”时期，Fe2+被大量取代为 Mg2+。在这里，我们证明了在缺氧环境中通过去除 Mg2+并用 Fe2+取代来逆转这种假定的金属取代，可扩展 RNA 的催化范围。Fe2+可以赋予某些 RNA 以前尚未被描述的催化单电子转移的能力。我们提出，与蛋白质功能类似，只有在与一系列可能的金属相关联的情况下，才能全面理解 RNA 的功能。电子转移的催化作用是代谢活动所必需的，而光合作用和氧气的出现可能削弱了 RNA 中的这种作用。
