The domain belongs to a fast evolving family known only from the placental mammals. The PGC7/Stella/Dppa3 protein protects imprinted regions from demethylation post-fertilization. This suggests that it might bind methylated DNA sequences directly. The conserved core includes a postively charged helical segment and a C-terminal CXCXXC motif that is predicted to chelate a metal ion. Most placental mammals contain 3-6 paralogs of this domain family. The CXCXXC motif is also conserved in a subset of fungal MBD4-like proteins.