2-methylpropanoyl-CoA + oxidized [electron-transfer flavoprotein] + H(+) => 2-methylpropenoyl-CoA + reduced [electron-transfer flavoprotein]
2-methylpropanoyl-coa + oxidized [electron-transfer flavoprotein] + h(+) => 2-methylpropenoyl-coa + reduced [electron-transfer flavoprotein]