The MIU (Motif Interacting with Ubiquitin) domain binds to ubiquitin in a manner almost identical to that of the UIM:Ub interaction, although in the opposite orientation.Similar to UIM domains, a critical Ala residue is required for binding to Ub. MIU-containing proteins have been reported to bind to polyUb chains linked through lysine-48 or lysine-63 of ubiquitin. The identification of MIU domains in proteins such as Myosin VI and Rabex-5 support their role in ubiquitin-dependant vesicular trafficking.