Anticodon binding domain (HGPT)

The anticodon binding domain HGPT recognises the tRNA anticodon loop, approaching the acceptor stem from the major groove side (Cusack et al. 1998, Sankaranarayanan et al. 1999, Tian et al. 2015). This compact domain consists of a five-stranded $\beta$ sheet and resides at the C-termini of four Class II AARS: [HisRS](/class2/his/), [ProRS](/class2/pro1/), [ThrRS](/class2/thr/), and the dimeric [GlyRS](/class2/gly1/). This domain was mostly likely transferred between subclasses IIa (ProRS, ThrRS, and GlyRS) and IIc (HisRS), which have quite distinct catalytic domains (Douglas et al. 2023). The remaining members of subclass IIa - [SerRS](/class2/ser1/) and [SerRS-A](/class2/ser2/) - are lacking this domain.

References

Tian, Qingnan, et al. "Structural basis for recognition of G-1-containing tRNA by histidyl-tRNA synthetase." Nucleic acids research 43.5 (2015): 2980-2990. Cusack, Stephen, et al. "tRNAPro anticodon recognition by Thermus thermophilus prolyl-tRNA synthetase." Structure 6.1 (1998): 101-108. Sankaranarayanan, Rajan, et al. "The structure of threonyl-tRNA synthetase-tRNAThr complex enlightens its repressor activity and reveals an essential zinc ion in the active site." Cell 97.3 (1999): 371-381. Douglas, J, Bouckaert, R., Carter, C., & Wills, P. R. Enzymic recognition of amino acids drove the evolution of primordial genetic codes. Research Square (2023).