Ubiquitin molecules that are either mutated in PD (PINK1, Parkin, and Fbxo7) or are a leading candidate for drug discovery (USP30) are depicted. PINK1: MTS, mitochondrial-targeting sequence; TMD, transmembrane domain; CTD, C-terminal domain. Parkin: Ubl, ubiquitin-like domain; RCat, required for catalysis; BRCat, Benign Rcat; Rep, Repressor element of Parkin. F-box07 (Fbx07): Ubl, ubiquitin-like domain; FP, Fbxo7 and PI31-interacting domain; PRR, proline-rich region. Ubiquitin-specific processing protease 30 (USP30): TMD, transmembrane domain; DUB, deubiquitinase domain.