catalytic core domain of isoleucyl, leucyl, valyl and methioninyl tRNA synthetases
Catalytic core domain of isoleucyl, leucyl, valyl and methioninyl tRNA synthetases. These class I enzymes are all monomers. However, in some species, MetRS functions as a homodimer, as a result of an additional C-terminal domain. These enzymes aminoacylate the 2'-OH of the nucleotide at the 3' of the appropriate tRNA. The core domain is based on the Rossman fold and is responsible for the ATP-dependent formation of the enzyme bound aminoacyl-adenylate. It contains the characteristic class I HIGH and KMSKS motifs, which are involved in ATP binding. Enzymes in this subfamily share an insertion in the core domain, which is subject to both deletions and rearrangements. This editing region hydrolyzes mischarged cognate tRNAs and thus prevents the incorporation of chemically similar amino acids. MetRS has a significantly shorter insertion, which lacks the editing function.
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