catalytic core domain of methioninyl-tRNA synthetases
Methionine tRNA synthetase (MetRS) catalytic core domain. This class I enzyme aminoacylates the 2'-OH of the nucleotide at the 3' of the appropriate tRNA. MetRS, which consists of the core domain and an anti-codon binding domain, functions as a monomer. However, in some species the anti-codon binding domain is followed by an EMAP domain. In this case, MetRS functions as a homodimer. 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. As a result of a deletion event, MetRS has a significantly shorter core domain insertion than IleRS, ValRS, and LeuR. Consequently, the MetRS insertion lacks the editing function.