This domain is found at the N-terminal end of Spermatogenesis- associated protein 2 from humans (SPATA2) and similar proteins from animals. This protein interacts with the deubiquitinase CYLD through its non-canonical PUB domain (this entry) and activates CYLD-mediated hydrolysis of ubiquitin chains. This domain shows an all-helical fold [1].

1: SPATA2 Links CYLD to LUBAC, Activates CYLD, and Controls LUBAC Signaling. Elliott PR, Leske D, Hrdinka M, Bagola K, Fiil BK, McLaughlin SH, Wagstaff J, Volkmar N, Christianson JC, Kessler BM, Freund SM, Komander D, Gyrd-Hansen M; Mol Cell. 2016;63:990-1005. PMID:27591049