How functional peptides may have arisen is a significant problem for the scenario of the RNA world. An attractive idea, the direct RNA template (DRT) hypothesis, proposes that RNA molecules can bind amino acids specifically and promote the synthesis of corresponding peptides, thereby starting the RNA/peptides world. To investigate the plausibility of this idea, we modeled the emergence of a “membrane-stabilizing peptide” in RNA-based protocells—such a peptide was suggested to have appeared early in the RNA world based on experimental evidence. The computer simulation demonstrated that the protocells containing the “RNA gene” encoding this peptide may spread in the system owing to the peptide’s function. The RNA gene may either originate de novo in protocells or emerge in protocells already containing ribozymes—here we adopt a nucleotide synthetase ribozyme as an example. Furthermore, interestingly, we show that a “nucleotide synthetase peptide” encoded by RNA (also via the DRT mechanism) may substitute the nucleotide synthetase ribozyme in evolution, which may represent how “functional-takeover” in the RNA world could have occurred. Overall, we conclude that the transition from the RNA world towards an RNA/peptides world may well have been mediated by the DRT mechanism. Remarkably, the successful modeling on the emergence of membrane-stabilizing peptide in RNA-based protocells is per se significant, which may imply a “promising” way for peptides to enter the RNA world, especially considering the weak interaction between RNA and the membrane in chemistry.

中文翻译：

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通过直接 RNA 模板机制迈向 RNA/肽世界：基于 RNA 的原始细胞中膜稳定肽的出现

对于 RNA 世界来说，功能性肽是如何产生的是一个重大问题。一个有吸引力的想法，直接RNA模板（DRT）假说，提出RNA分子可以特异性结合氨基酸并促进相应肽的合成，从而开启RNA/肽世界。为了研究这个想法的合理性，我们模拟了基于 RNA 的原始细胞中“膜稳定肽”的出现——根据实验证据，这种肽被认为很早就出现在 RNA 世界中。计算机模拟表明，含有编码该肽的“RNA基因”的原始细胞可能由于该肽的功能而在系统中扩散。 RNA基因可能起源于原始细胞，也可能出现在已经含有核酶的原始细胞中——这里我们以核苷酸合成酶核酶为例。此外，有趣的是，我们发现RNA编码的“核苷酸合成酶肽”（也通过DRT机制）可能在进化中取代核苷酸合成酶核酶，这可能代表了RNA世界中“功能接管”是如何发生的。总的来说，我们得出的结论是，从 RNA 世界到 RNA/肽世界的转变很可能是由 DRT 机制介导的。值得注意的是，对基于 RNA 的原始细胞中膜稳定肽的出现的成功建模本身就具有重要意义，这可能意味着肽进入 RNA 世界的一种“有前途”的方式，特别是考虑到 RNA 与细胞膜之间的弱相互作用。化学。