Figure 6.

Three-dimensional structure of rQR₁ in complex with FAD and NADP⁺ (12). The C-terminal 43 amino acids (232–274) are shown in red (Left), and have been truncated at the arrow (Right). Different colors of the backbone indicate the two different subunits. It can be seen that the truncated portion of QR₂ is critical for binding of the pyrophosphate moiety of the NAD(P)H cofactor. Note that the contact regions between the enzyme and FAD are presumably preserved in QR₂ (Right), consistent with the tight binding of FAD. The structural comparison between rQR₁ and hQR₂ is appropriate since the homology between rQR₁ and hQR₁ is very high (85% identity).