Threonine—tRNA ligase

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threonine-tRNA ligase
Identifiers
ExPASy
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KEGGKEGG entry
MetaCycmetabolic pathway
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In

enzymology, a threonine-tRNA ligase (EC 6.1.1.3) is an enzyme that catalyzes the chemical reaction

ATP + L-threonine + tRNA(Thr) AMP + diphosphate + L-threonyl-tRNA(Thr)

The three

diphosphate
, and L-threonyl-tRNA(Thr).

The systematic name of this enzyme class is L-threonine:tRNAThr ligase (AMP-forming). Other names in common use include threonyl-tRNA synthetase, threonyl-transfer ribonucleate synthetase, threonyl-transfer RNA synthetase, threonyl-transfer ribonucleic acid synthetase, threonyl ribonucleic synthetase, threonine-transfer ribonucleate synthetase, threonine translase, threonyl-tRNA synthetase, and TARS.

Threonine—tRNA ligase (TARS) belongs to the family of

anticodon embedded in the tRNA. During their long evolution, some of these enzymes have acquired additional functions, including roles in RNA splicing, RNA trafficking, transcriptional regulation, translational regulation, and cell signaling
.

Structural studies

As of late 2007, 17

structures have been solved for this class of enzymes, with PDB accession codes 1EVK, 1EVL, 1FYF, 1KOG, 1NYQ, 1NYR, 1QF6, 1TJE, 1TKE, 1TKG, 1TKY, 1WWT, 1Y2Q, 2HKZ, 2HL0, 2HL1, and 2HL2
.

Translational regulation

Threonyl-tRNA synthetase (TARS) from Escherichia coli is encoded by the thrS

operator, can be folded into four distinct domains.[2] Each of domains 2 and 4 can be folded in a stem and loop structure that mimics the anticodon arm of E. coli tRNA(Thr). Mutagenesis and biochemical experiments have shown that the two anticodon-like domains of the operator bind to the two tRNA(Thr) anticodon recognition sites (one per subunit) of the dimeric TARS in a quasi-symmetrical manner.[3][4]

The crystal structures of (i) TARS complexed with two tRNA(Thr) molecules,[5] and (ii) TARS complexed with two isolated domains 2,[6] have confirmed that TARS recognition is primarily governed by similar base-specific interactions between the anticodon loop of tRNA(Thr) and the loop of the operator domain 2. The same amino acids interact with the CGU anticodon sequence of tRNA(Thr) and the analogous residues in domain 2.

References

Further reading