a ubiquinone + reduced [electron-transfer flavoprotein] <=> a ubiquinol + oxidized [electron-transfer flavoprotein] + H(+)
a ubiquinone + reduced [electron-transfer flavoprotein] <=> a ubiquinol + oxidized [electron-transfer flavoprotein] + h(+)
a ubiquinone + reduced [electron-transfer flavoprotein] <=> a ubiquinol + oxidized [electron-transfer flavoprotein] + H(+)
a ubiquinone + reduced [electron-transfer flavoprotein] <=> a ubiquinol + oxidized [electron-transfer flavoprotein] + h(+)