Accepts electrons from ETF and reduces ubiquinone. a ubiquinone + reduced [electron-transfer flavoprotein] = a ubiquinol + H(+) + oxidized [electron-transfer flavoprotein] Binds 1 [4Fe-4S] cluster. Monomer. Acetylation of Lys-95 and Lys-222 is observed in liver mitochondria from fasted mice but not from fed mice. Belongs to the ETF-QO/FixC family.