(A) The substrate envelope (red surface) and binding (blue mesh) envelope volumes are illustrated for substrate residues P3-P3'. Drug resistant mutation residues 30, 47, 48, 50, 82, and 84 are shown as sticks. (B) The inhibitor volume consisting of the combined volumes of inhibitors Nelfinavir, Saquinavir, Indinavir, Ritonavir, Amprenavir, Lopinavir, and Atazanavir, is shown in orange.