1DIF

HIV-1 PROTEASE IN COMPLEX WITH A DIFLUOROKETONE CONTAINING INHIBITOR A79285

Summary for 1DIF

• Entry DOI: 10.2210/pdb1dif/pdb
• Descriptor: HIV-1 PROTEASE, BETA-MERCAPTOETHANOL, N-{1-BENZYL-2,2-DIFLUORO-3,3-DIHYDROXY-4-[3-METHYL-2-(3-METHYL-3-PYRIDIN-2-YLMETHYL-UREIDO)-BUTYRYLAMINO]-5-PHENYL-PENTYL}-3-METHYL-2-(3-METHYL-3-PYRIDIN-2-YLMETHYL-UREIDO)-BUTYRAMIDE, ... (4 entities in total)
• Functional Keywords: aspartic proteinase
• Biological source: Human immunodeficiency virus 1
• Cellular location: Matrix protein p17: Virion (Potential). Capsid protein p24: Virion (Potential). Nucleocapsid protein p7: Virion (Potential). Reverse transcriptase/ribonuclease H: Virion (Potential). Integrase: Virion (Potential): P03367
• Total number of polymer chains: 2
• Total formula weight: 22594.74

Authors

Silva, A.M.,Cachau, R.E.,Sham, H.L.,Erickson, J.W. (deposition date: 1995-10-09, release date: 1996-03-08, Last modification date: 2024-06-05)

Primary citation

Silva, A.M.,Cachau, R.E.,Sham, H.L.,Erickson, J.W.
Inhibition and catalytic mechanism of HIV-1 aspartic protease.
J.Mol.Biol., 255:321-346, 1996

PubMed Abstract: The structure of the HIV-1 protease in complex with a pseudo-C2 symmetric inhibitor, which contains a central difluoroketone motif, has been determined with X-ray diffraction data extending to 1.7 A resolution. The electron density map clearly indicates that the inhibitor is bound in a symmetric fashion as the hydrated, or gemdiol, form of the difluoroketone. Refinement of the complex reveals a unique, and almost symmetric, set of interactions between the geminal hydroxyl groups, the geminal fluorine atoms, and the active-site aspartate residues. Several hydrogen bonding patterns are consistent with that conformation. The lowest energy hydrogen disposition, as determined by semiempirical energy calculations, shows only one active site aspartate protonated. A comparison between the corresponding dihedral angles of the difluorodiol core and those of a hydrated peptide bond analog, calculated ab-initio, shows that the inhibitor core is a mimic of a hydrated peptide bond in a gauche conformation. The feasibility of an anti-gauche transition for a peptide bond after hydration is verified by extensive molecular dynamics simulations. The simulations suggest that rotation about the C-N scissile bond would readily occur after hydration and would be driven by the optimization of the interactions of peptide side-chains with the enzyme. These results, together with the characterization of a transition state leading to bond breakage via a concerted exchange of two protons, suggest a proteolysis mechanism whereby only one active site aspartate is initially protonated. The steps of this mechanism are: asymmetric binding of the substrate; hydration of the peptidic carbonyl by an active site water; proton translocation between the active site aspartate residues simultaneously with carbonyl hydration; optimization of the binding of the entire substrate facilitated by the flexible structure of the hydrated peptide bond, which, in turn, forces the hydrated peptide bond to assume a gauche conformation; simultaneous proton exchange whereby one hydroxyl donates a proton to the charged aspartate, and, at the same time, the nitrogen lone pair accepts a proton from the other aspartate; and, bond breakage and regeneration of the initial protonation state of the aspartate residues.

PubMed: 8551523
DOI: 10.1006/jmbi.1996.0026

Experimental method

X-RAY DIFFRACTION (1.7 Å)