RNAが生み出すアミノ酸の分子非対称性

概要

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Although living organisms have a symmetrical appearance at the macroscopic level, biological systems are composed of typical asymmetrical molecules: nucleic acids (RNA and DNA) have ribose with D-configuration while proteins have alpha-carbons with L-configuration. However, the origin of biomolecular homochirality is still unknown. Proteins are synthesized on the ribosome by the elongation of L-amino acids that are attached to tRNAs. Therefore, aminoacylation of tRNA could be the key step in the origin of amino acid homochirality. With this in mind, we attempted non-enzymatic aminoacylation of an RNA minihelix (primordial tRNA) with an aminoacyl-phosphate-D-oligonucleotide, which revealed chiral-selective aminoacylation of the RNA minihelix with a clear preference for L-amino acids. A mirror-image RNA system with L-ribose exhibited aminoacylation with the preference for D-amino acids. These results suggest that the stereochemistry of RNA could be the determinant of chiral-selectivity of amino acids. The D-ribose-based "RNA world" was probably established by chiral-selective ligation of oligonucleotides, which would have generated a "winner" sequence with an important chemical ability for evolution of life.
2011-06-01