MeCP2, MBD1, MBD2, MBD3, MBD4, CLLD8-like, and BAZ2A-like proteins constitute a family of proteins that share the methyl-CpG-binding domain (MBD). The MBD consists of about 70 residues and is defined as the minimal region required for binding to methylated DNA by a methyl-CpG-binding protein which binds specifically to methylated DNA. The MBD can recognize a single symmetrically methylated CpG either as naked DNA or within chromatin. MeCP2, MBD1 and MBD2 (and likely MBD3) form complexes with histone deacetylase and are involved in histone deacetylase-dependent repression of transcription. MBD4 is an endonuclease that forms a complex with the DNA mismatch-repair protein MLH1. The MBDs present in putative chromatin remodelling subunit, BAZ2A, and putative histone methyltransferase, CLLD8, represent two phylogenetically distinct groups within the MBD protein family.