期刊
JOURNAL OF MOLECULAR BIOLOGY
卷 428, 期 13, 页码 2780-2792出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmb.2016.05.005
关键词
HIV protease; drug resistance; protein folding landscape; high-pressure NMR; calorimetry
资金
- Intramural Research Program of the NIDDK, National Institutes of Health
- Intramural AIDS-Targeted Program of the Office of the Director, NIH
Using high-pressure NMR spectroscopy and differential scanning calorimetry, we investigate the folding landscape of the mature HIV-1 protease homodimer. The cooperativity of unfolding was measured in the absence or presence of a symmetric active site inhibitor for the optimized wild type protease (PR), its inactive variant PRD25N, and an extremely multidrug-resistant mutant, PR20. The individual fit of the pressure denaturation profiles gives rise to first order, Delta G(NMR), and second order, Delta V-NMR (the derivative of Delta G(NMR) with pressure); apparent thermodynamic parameters for each amide proton considered. Heterogeneity in the apparent Delta V-NMR values reflects departure from an ideal cooperative unfolding transition. The narrow to broad distribution of Delta V-NMR spanning the extremes from inhibitor-free PR20(D25N) to PR-DMP323 complex, and distinctively for PRD25N-DMP323 complex, indicated large variations in folding cooperativity. Consistent with this data, the shape of thermal unfolding transitions varies from asymmetric for PR to nearly symmetric for PR20, as dimer-inhibitor ternary complexes. Lack of structural cooperativity was observed between regions located close to the active site, including the hinge and tip of the glycine-rich flaps, and the rest of the protein. These results strongly suggest that inhibitor binding drastically decreases the cooperativity of unfolding by trapping the closed flap conformation in a deep energy minimum. To evade this conformational trap, PR20 evolves exhibiting a smoother folding landscape with nearly an ideal two-state (cooperative) unfolding transition. This study highlights the malleability of retroviral protease folding pathways by illustrating how the selection of mutations under drug pressure remodels the free-energy landscape as a primary mechanism. Published by Elsevier Ltd.
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