LysRS1

LysRS1, or lysyl-tRNA synthetase type I, is an aminoacyl-tRNA synthetase that charges tRNA^Lys with the amino acid lysine during protein synthesis. It belongs to the class I family of aaRS and is structurally distinct from LysRS2, which is a class II enzyme. LysRS1 is found in certain archaea and bacteria, and in some organisms it coexists with LysRS2, where the two enzymes may have different regulatory roles or substrate specificities. In many bacteria, LysRS2 is the sole lysyl-tRNA synthetase, while LysRS1 can be present as a paralog in others.

Enzymatic function: LysRS1 catalyzes the ATP-dependent activation of lysine to lysyl-adenylate (Lys-AMP) and transfers lysine to tRNA^Lys, yielding Lys-tRNA^Lys and AMP, with pyrophosphate formed during the activation step. The reaction requires Mg2+ as a cofactor and uses tRNA^Lys as the substrate. Substrate recognition involves elements of the tRNA^Lys identity determinants, and as a class I enzyme, LysRS1 typically contains the conserved HIGH and KMSKS motifs within its catalytic core.

Structure and evolution: LysRS1 adopts a Rossmann-like catalytic fold characteristic of class I aaRSs. Its existence alongside LysRS2 reflects an ancient divergence of lysyl-tRNA synthetase lineages, and the two enzymes are not homologous. The distribution of LysRS1 is patchy across species, suggesting lineage-specific retention or loss and potential functional specialization under different environmental conditions.

See also: aminoacyl-tRNA synthetases; LysRS2.