Family of ATP-grasp enzymes belonging to the R2K clade, wherein one of the absolutely-conserved lysine residues has migrated to the RAGYNA domain which is a part of the core ATP-grasp module. This family is predicted to catalyze peptide ligation reactions on protein substrates in biological conflict contexts, probably between bacteriophages and their hosts [1].

1: The eukaryotic translation initiation regulator CDC123 defines a divergent clade of ATP-grasp enzymes with a predicted role in novel protein modifications. Burroughs AM, Zhang D, Aravind L; Biol Direct. 2015;10:21. PMID:25976611