Abstract

Proteins are composed of 20 kinds of amino acids. Aminoacyl tRNA, in which an amino acid is covalently bound to 3’ end of tRNA, carries the “right” amino acid onto the ribosome where translation occurs. Commonly, it is thought that at least 20 sets of aminoacyl-tRNA synthetases (aaRS) are required for accurate protein biosynthesis. But none of archaea and bacterial organelle has perfect sets of canonical aaRSs; that is, they lack glutaminyl-tRNA synthetase (GlnRS), asparaginyl-tRNA synthetase (AsnRS), lysyl-tRNA synthetase (LysRS), and cysteinyl-tRNA synthetase (CysRS) in methanogenic archaea. It would be noteworthy that archaea, which is thought to be the origin of life or close to it, has such an “odd” translation system. I would like to introduce the unique translation system in archaea and talk about the mysterious origin of genetic code based on recent biochemical and structural evidence.

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