Structural domains comprising this superfamily share the structure of the C-terminal domain of leucyl/phenylalanyl-tRNA-protein transferases (L/F-transferases), an N-end rule pathway enzyme, involved in the transfer of Leu and Phe from aminoacyl-tRNAs to exposed N-terminal Arg or Lys residues of acceptor proteins PMID:17891155. This C-terminal domain has a highly conserved fold, observed in the GCN5-related N-acetyltransferase (GNAT) family.

The interface of the N-terminal and C-terminal domains forms a large central cavity, with the characteristic positive charge contributed by the corner of the cleft on the C-terminal domain surface, suggesting that they probably complement the negatively charged phosphate backbone of the substrate aminoacyl-tRNA PMID:17242373.