Members of this family of ubiquitin binding domains adopt a structure consisting of a three alpha-helix bundle. They are predominantly found in fungal ubiquitin-protein ligases [1].

1: Solution structure of the flexible class II ubiquitin-conjugating enzyme Ubc1 provides insights for polyubiquitin chain assembly. Merkley N, Shaw GS; J Biol Chem. 2004;279:47139-47147. PMID:15328341