Fig. 25.

The CYP450 3A4 substrate binding site. (A) Ritonavir in the substrate binding site of CYP450 3A4. Taken from the 3NXU crystal structure [118]. (B) The variability in the shape of the substrate binding site. All nine structures are superimposed and equivalent residues coloured the same. The haem and ritonavir from the 3NXU structure are shown. In both figures the haem is shown in purple and the ritonavir in cyan. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)