catalytic core domain of class I lysyl tRNA synthetase
Class I lysyl tRNA synthetase (LysRS) catalytic core domain. This class I enzyme is a monomer which aminoacylates 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. The class I LysRS is found only in archaea and some bacteria and has evolved separately from class II LysRS, as the two do not share structural or sequence similarity.