Schematic diagram for the subunit structures of acetyl-CoA carboxylases. Abbreviations and symbols: CBBS, carboxybiotin-binding site; Acyl-CoA, acyl-CoA-binding site; ATP, ATP-binding site; CO2, CO2 fixation site; ●, biotin-binding site; ACC, acetyl-CoA carboxylase; CT, carboxyltransferase; BCCP, biotin carboxyl carrier protein; BC, biotin carboxylase.