This domain appears to be a zinc finger. The alignment shows four conserved cysteine residues and a conserved tryptophan. It was first identified by, and is predicted to be a "highly specialized mononuclear four-cysteine zinc finger...that plays a role in DNA binding and/or promoting protein-protein interactions in complicated eukaryotic processes including...chromatin methylation status and early embryonic development." Weak homology to pfam00628 further evidences these predictions (personal obs: C Yeats). Twelve different CW-domain-containing protein subfamilies are described, with different subfamilies being characteristic of vertebrates, higher plants and other animals in which these domain is found.