Caught in the Act: The 1.5 Å Resolution Crystal Structures of the HIV-1 Protease and the I54V Mutant Reveal a Tetrahedral Reaction Intermediate
- GSU
HIV-1 protease (PR) is the target for several important antiviral drugs used in AIDS therapy. The drugs bind inside the active site cavity of PR where normally the viral polyprotein substrate is bound and hydrolyzed. We report two high-resolution crystal structures of wild-type PR (PR{sub WT}) and the multi-drug-resistant variant with the I54V mutation (PR{sub I54V}) in complex with a peptide at 1.46 and 1.50 {angstrom} resolution, respectively. The peptide forms a gem-diol tetrahedral reaction intermediate (TI) in the crystal structures. Distinctive interactions are observed for the TI binding in the active site cavity of PR{sub WT} and PR{sub I54V}. The mutant PR{sub I54V}/TI complex has lost water-mediated hydrogen bond interactions with the amides of Ile50 and Ile50{prime} in the flap. Hence, the structures provide insight into the mechanism of drug resistance arising from this mutation. The structures also illustrate an intermediate state in the hydrolysis reaction. One of the gem-diol hydroxide groups in the PR{sub WT} complex forms a very short (2.3 {angstrom}) hydrogen bond with the outer carboxylate oxygen of Asp25. Quantum chemical calculations based on this TI structure are consistent with protonation of the inner carboxylate oxygen of Asp25{prime}, in contrast to several theoretical studies. These TI complexes and quantum calculations are discussed in relation to the chemical mechanism of the peptide bond hydrolysis catalyzed by PR.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 1007635
- Journal Information:
- Biochemistry-US, Vol. 46, Issue (51) ; 2007; ISSN 0006-2960
- Country of Publication:
- United States
- Language:
- ENGLISH
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