Catalyzes the attachment of threonine to tRNA(Thr) in a two-step reaction: threonine is first activated by ATP to form Thr-AMP and then transferred to the acceptor end of tRNA(Thr) (PubMed:25824639, PubMed:31374204). Also edits incorrectly charged tRNA(Thr) via its editing domain, at the post-transfer stage (By similarity). ATP + L-threonine + tRNA(Thr) = AMP + diphosphate + H(+) + L-threonyl-tRNA(Thr) Inhibited by borrelidin (BN, IC 50 is 7 nM), which binds to 4 distinct subsites in the protein, preventing binding of all 3 substrates (PubMed:25824639). Homodimer. ISGylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the class-II aminoacyl-tRNA synthetase family. Truncated N-terminus.