CRYSTAL-STRUCTURES OF COMPLEXES OF A PEPTIDIC INHIBITOR WITH WILD-TYPE AND 2 MUTANT HIV-1 PROTEASES

Crystal structures of the protease of human immunodeficiency virus typ e 1 (HIV-1) and two mutant proteases, V82D and V82N, have been determi ned. In all three cases the enzyme forms a complex with the peptidic i nhibitor U-89360E. All structures have been determined to 2.3 Angstrom resolution and have satisfactory agreement factors: 0.173 for wild ty pe, 0.175 for V82D, and 0.182 for V82N. Comparison of the three crysta l structures provides explanations which are consistent with the known kinetic properties of these mutant enzymes with the U-89360E inhibito r [Lin, Y., Lin, X., Hong, L., Foundling, S., Heinrikson, R. L., Thais rivongs, S., Leelamanit, W., Raterman, D., Shah, M., Dunn, B. M., & Ta ng, J. (1995) Biochemistry 34, 1143-1152]. Unfavorable van der Waals i nteractions between the inhibitor and the mutated side chains at posit ion 82 are consistent with diminished affinity for the inhibitor by th e mutant enzymes. If a mutation is potentially resistant to an inhibit or, the mutant enzyme should not only have an increased K-i for the in hibitor but should also preserve considerable catalytic capability. Th e V82D mutant possesses these qualities. In the V82D crystal structure , a water molecule, which connects the protease flap to the inhibitor, is missing or of low occupancy. Absence of this bridge may be importa nt in determining catalytic capability. Moreover, mutation at position 82 induces change in two polypeptide backbone regions, 35-41 and 67-6 8, which may be related to protease flap mobility.