Proteins in this family have been described as probable nuclear receptor interacting proteins. The C-terminal domain of this family is homologous to the retroviral aspartyl protease domain. The domain is structurally related to one lobe of the pepsin molecule. The conserved active site aspartate occurs within a motif (Asp-Thr/Ser-Gly), as it does in pepsin. Asp residues are ligands of an activated water molecule in all examples where catalytic residues have been identified. This group of aspartate peptidases is classified by MEROPS as the peptidase family A2 (retropepsin family, clan AA), subfamily A2A.