This Jmol page shows the structure of wild-type (right panel) HIV protease bound to an inhibitor (HIV drug). In this complex, a number of non-polar residues of the protease make extensive contacts the inhibitor, providing a hydrophobic binding pocket that stabilizes the drug-enzyme complex. The presence of the drug in the active site prevents the protease from binding its normal substrate. The middle panel shows a mutation of the HIV protease that no longer binds the drug. The right panel shows a redesigned drug, forming good contacts with the mutant enzyme.