BAH: Owing to extensive intermolecular contacts, the ankyrin repeats of G9a and GLP and the BAH domain of ORC1 show high specificity for di- or monomethylated H3K9 and H4K20me2, respectively. The H3K9me2 peptide is sandwiched between the β-turns and α-helices of the fourth and fifth ankyrin repeats, whereas K9me2 fits into the aromatic cage also containing a glutamate. (1)

Reference
1. Musselman CA, Lalonde ME, Cote J, Kutateladze TG.Perceiving the epigenetic landscape through histone readers. Nat Struct Mol Biol.2012;19(12):1218-27. PMID: 23211769.