The discovery of chiral-selective aminoacylation of RNA minihelix has shown the possibility that the D-ribose-based “RNA world” was probably established first and that the stereochemistry of RNA could be the determinant of chiral-selectivity of amino acids. Aminoacylation of tRNA could be the key step in the origin of amino acid homochirality and once L-amino acids had been selected, the elongation of L-amino acids by the ribosome would have synthesized proteins composed of L-amino acids. However, in considering the structural features of both nucleotides and amino acids, the idea of “RNA world” first would need to be altered. Rather, the stereochemistry of nucleotides and amino acids are interdependent and biological homochirality could have been determined through the process of coevolution between nucleotides and amino acids.
The chirality of biopolymer has been one of the most important open questions in the origin of life. Some experiments of evolutionary molecular engineering have suggested that the function of a biopolymer does not depend on its chirality. Thus, the chirality of biopolymers might depend on the synthetic process of the biopolymer units (e.g., nucleotides, amino acids) before the RNA world.