title: Structural basis for specificity of retroviral proteases.
abstract: The Rous sarcoma virus (RSV) protease S9 variant has been engineered to exhibit high affinity for HIV-1 protease substrates and inhibitors in order to verify the residues deduced to be critical for the specificity differences. The variant has 9 substitutions (S38T, I42D, I44V, M73V, A100L, V104T, R105P, G106V, and S107N) of structurally equivalent residues from HIV-1 protease. Unlike the wild-type enzyme, RSV S9 protease hydrolyzes peptides representing the HIV-1 protease polyprotein cleavage sites. The crystal structure of RSV S9 protease with the inhibitor, Arg-Val-Leu-r-Phe-Glu-Ala-Nle-NH2, a reduced peptide analogue of the HIV-1 CA-p2 cleavage site, has been refined to an R factor of 0.175 at 2.4-A resolution. The structure shows flap residues that were not visible in the previous crystal structure of unliganded wild-type enzyme. Flap residues 64-76 are structurally similar to residues 47-59 of HIV-1 protease. However, residues 61-63 form unique loops at the base of the flaps. Mutational analysis indicates that these loop residues are essential for catalytic activity. Side chains of flap residues His 65 and Gln 63' make hydrogen bond interactions with the inhibitor P3 amide and P4' carbonyl oxygen, respectively. Other interactions of RSV S9 protease with the CA-p2 analogue are very similar to those observed in the crystal structure of HIV-1 protease with the same inhibitor. This is the first crystal structure of an avian retroviral protease in complex with an inhibitor, and it verifies our knowledge of the molecular basis for specificity differences between RSV and HIV-1 proteases.
authors.affiliation: Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: J M
authors.initials: JM
authors.lastname: Adomat
authors.forename: T W
authors.initials: TW
authors.lastname: Ridky
authors.forename: J M
authors.initials: JM
authors.lastname: Louis
authors.forename: J
authors.initials: J
authors.lastname: Leis
authors.forename: R W
authors.initials: RW
authors.lastname: Harrison
authors.forename: I T
authors.initials: IT
authors.lastname: Weber
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D016333:HIV Protease / Q000235:genetics / Q000378:metabolism; D017320:HIV Protease Inhibitors / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006860:Hydrogen Bonding; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D017320:HIV Protease Inhibitors; D009842:Oligopeptides; D010446:Peptide Fragments; D011994:Recombinant Proteins; C111508:arginyl-valyl-leucyl-r-phenylalanyl-glutamyl-alanyl-norleucinamide; D016282:Aspartic Acid Endopeptidases; D016333:HIV Protease; C072891:Rous sarcoma virus protease