Threonyl-tRNA Synthetase

Threonyl-tRNA synthetase (ThrRS) is an enzyme that plays a crucial role in protein synthesis by catalyzing the attachment of the amino acid threonine to its cognate tRNA: $ \text{Thr} + \text{tRNA}^\text{Thr} + \text{ATP} \xrightarrow{\text{ThrRS}} \text{Thr-tRNA}^\text{Thr} + \text{AMP} + \text{PP}_i $ ThrRS belongs to subclass IIa, which includes other enzymes such as [ProRS](/class2/pro1), [SerRS](/class2/ser1), and the dimeric [GlyRS](/class2/gly1) (Gomez et al. 2020, Valencia-Sánchez et al. 2016, Perona et al. 2012). The [anticodon binding domains](/superfamily/class2/Anticodon_binding_domain_HGPT) of subclass IIa, with the exception of SerRS, are homologous with that of [HisRS](/class2/his), and are located at the C-terminal end (Wolf et al. 1999). The catalytic domain of ThrRS is typical of a Class II aminoacyl-tRNA synthetase. Like most members of the superfamily, ATP binding is coordinated by the arginine tweezers, located in motifs 2 and 3 (Kaiser et al. 2018). The catalytic domain is characterized by the ~40 residue ThrRS insertion module which resides between motifs 2 and 3, and is stabilized by a short $\beta$ strand that runs parallel with the six stranded antiparallel fold of the catalytic domain (Douglas et al. 2023). This module, also known as the threonine loop, undergoes large conformational changes upon threonine binding (Torres-Larios et al. 2003). ThrRS also has an editing function, which occurs at the post-transfer level to remove mischarged serines from tRNA$^\text{Thr}$ (Dock-Bregeon et al. 2000). This is achieved through the two N-terminal domains N1 and N2 (Dock-Bregeon et al. 2004). The [editing domain](/superfamily/class2/Editing_domain_AT/) (N2) is homologous with that of [AlaRS](/class2/ala), which is conversely located downstream of the catalytic domain (Sankaranarayanan et al. 1999). In some archaea, a non-homologous N-terminal editing domain, which also targets mischarged serine, is present instead of the N1 and N2 domains in ThrRS (Hussain et al. 2006)

References

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