The former is generally dependent on ubiquitylation of OMM proteins by the RING-between-RING (RBR) ubiquitin–protein ligase parkin (encoded by PRKN) and PINK1, both of which are mutated in some forms of hereditary Parkinson's disease (McWilliams and Muqit, 2017). Here, PRKN is linked to Parkinson disease.