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Publication Abstract from PubMed

The mature HIV-1 protease (PR) bearing drug-resistance mutation L76V (PRL76V) is significantly less stable, with >7-fold higher dimer dissociation constant (Kd) of 71 +/- 24 nM and twice the sensitivity to urea denaturation (UC50 = 0.85 M) relative to PR. Differential scanning calorimetry showed a decrease in Tm of 12 degrees C for PRL76V in the absence of inhibitors, and 5-7 degrees C in the presence of inhibitors darunavir (DRV), saquinavir (SQV) and lopinavir (LPV), relative to PR. Isothermal titration calorimetry gave a ligand dissociation constant of 0.8 nM for DRV, ~160-fold larger than that of PR, consistent with DRV resistance. Crystal structures of PRL76V complexed with DRV and SQV were determined at resolutions of 1.45-1.46 A. Compared to the corresponding PR complexes, the mutated Val76 lacks hydrophobic interactions with Asp30, Lys45, Ile47, and Thr74, and exhibits closer interactions with Val32 and Val56. The bound DRV lacks one hydrogen bond with the main chain of Asp30 in PRL76V relative to PR, possibly accounting for resistance to DRV. SQV shows slightly improved polar interactions with PRL76V compared to PR. Although the L76V mutation significantly slows the N-terminal autoprocessing of the precursor TFR-PRL76V to give rise to the mature PRL76V, the co-selected M46I mutation counteracts by enhancing this rate but renders the TFR-PRM46I/L76V precursor less responsive to inhibition by 6 microM LPV while retaining inhibition by SQV and DRV. The correlation of lowered stability, higher Kd and impaired autoprocessing, with reduced internal hydrophobic contacts suggests a novel molecular mechanism for drug resistance.

Drug Resistance Mutation L76V Decreases the Dimer Stability and Rate of Autoprocessing of HIV-1 Protease by Reducing Internal Hydrophobic Contacts.,Louis JM, Zhang Y, Sayer JM, Wang YF, Harrison RW, Weber IT Biochemistry. 2011 Mar 29. PMID:21446746^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.