The DUIM proteins form a single a-helix, which binds two ubiquitin molecules, one on either side. These two ubiquitin molecules are related by pseudo two-fold screw symmetry along the helical axis of the UIM, corresponding to a shift by two residues on the UIM helix. DUIMs belongs to a new subclass of double-sided UIMs (1).

1. Hirano et al., 2006. Double-sided ubiquitin binding of Hrs-UIM in endosomal protein sorting. Nat Struct Mol Biol., 13(3):272-7. PMID: 16462748