“…However, the ABDs of aaRS are diverse in structure, the ABD with a four‐helix bundle is observed in MetRS, IleRS, ValRS, LeuRS, CysRS and ArgRS [3]; the ABD of GlnRS is composed of two β‐barrel domains, but the ABDs of GluRS and LysRS‐I contain two all α‐helix domains [4]; the TyrRS_ABD comprises α + β structure; the α‐helix bundle ABD is observed at the C‐terminal of TrpRS; in ProRS, ThrRS, HisRS and glycyl‐tRNA synthetase (GlyRS), their ABDs with α/β fold structure are located at the C‐terminal; the ABDs of LysRS‐II, AspRS and AsnRS are at N‐terminal and share a β‐barrel (OB‐fold) structure [5]. The SerRS is an exceptional case, in which its N‐terminal coil domain interacts with the long variable arm of tRNA Ser , but the both anticodon loop and acceptor arm can not be recognized by SerRS [6]. It is generally believed that the primitive aaRS only contains a domain (CCD), and the ABD would be added to the N‐ or C‐terminal of CCD later; because of the ABDs’ help, the enzymes obtained the capacity to discriminate diverse tRNA specificities [7].…”