 The NTase domain, conserved in capping enzymes, DNA and RNA ligases, is made up 5 motifs, I, III, IIIa, IV and V. Motif I or KxDG is the active site where the covalent (lysyl)-N-GMP intermediate is formed.Both the NTase and OB domains undergo conformational changes that assist in the capping reaction.Capping enzymes are found in the nucleus of eukaryotic cells.