MUL1 is an E3 ubiquitin-protein ligase with a RING finger domain that controls mitochondrial morphology, fragmentation and localization. E3 ubiquitin ligases accept the component ubiquitin from a donor E2 ubiquitin-conjugating directly transfer this ubiquitin to designated targeted substrates. The largest, proteome-wide and site-specific quantitative mapping dataset assessment of endogenous putative ubiquitylation sites and regulation was executed by Wagner’s group in Denmark1.