PRKN and Parkinson disease: Parkin, an E3 ligase associated with Parkinson’s disease (Kitada et al., 1998), belongs to the RING-between-RING family of E3 ligases (Smit and Sixma, 2014; Walden and Rittinger, 2018): it has an N-terminal Ub-like (UBL) domain, a zinc-binding domain (RING0, unique to Parkin), a RING domain (RING1, a canonical domain), and two linear zinc-binding folds (IBR and RING2; Panicker et al., 2017).