MT-ND4 and Parkinson disease: Other studies have shown that some core (ND4, ND5, NDUFS1, NDUFS2, and NDUFV1) and accessory (NDUFB5, NDUFB6, and NDUFB7) subunits are oxidatively damaged in PD brains, resulting in CI misassembling and functional impairment (Keeney et al., 2006).