MBT: MBT reads lower methylation states, recognizing mono- and dimethylated lysines. All MBTs characterized at present contain two to four repeats of ~100 amino acids. The most common three-repeat 3MBT module folds in a propeller-like structure, and the four-repeat 4MBT module has an asymmetric rhombus architecture29-32. Notably, although each MBT repeat contains an aromatic cage, which also includes an acidic residue, only the second repeat binds methyllysine. (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.