Based on limited published evidence, PYURF (PIGY upstream open reading frame) is an S-adenosylmethionine-dependent methyltransferase chaperone localized to mitochondria. It stabilizes components of coenzyme Q biosynthesis, including COQ5, and supports complex I (NADH:ubiquinone oxidoreductase) assembly by stabilizing assembly factors such as NDUFAF5 1. PYURF interacts with NDUFAF5 2, and disruption of PYURF has been associated with previously unresolved multisystemic mitochondrial disorders 1.