Structure prediction of ETF:QO. (A) The predicted wild-type model of human ETF:QO. The structure comprises three domains: the FAD-binding domain (gray), the ubiquinone-binding domain (blue) and the 4Fe4S cluster domain (red). The three redox centers: FAD, ubiquinone and the 4Fe4S cluster are shown in ball-and-stick representations. A cluster of hydrophobic residues which are located at the FAD-binding domain and at a distance below 4 Å around the mutation residues (p.Ala84Thr and p.Phe128Ser) are depicted in the sphere model. (B) A close-up view of the hydrophobic residues (V71, I73, A84, V85, L87, V100, L127 and F128). The α-helices and β-strands are also labeled. (C) Model of the p.Ala84Thr mutant in which the hydrophobic residue A84 is replaced by the hydrophilic residue threonine (yellow). (D) Model of the Phe128Ser mutant in which the hydrophobic residue F128 is replaced by the hydrophilic residue serine (yellow). The 3D molecular graphs are displayed using PyMOL .