1K2B: Combining Mutations In Hiv-1 Protease To Understand Mechanisms Of Resistance

HIV-1 develops resistance to protease inhibitors predominantly by selecting mutations in the protease gene. Studies of resistant mutants of HIV-1 protease with single amino acid substitutions have shown a range of independent effects on specificity, inhibition, and stability. Four double mutants, K45I/L90M, K45I/V82S, D30N/V82S, and N88D/L90M were selected for analysis on the basis of observations of increased or decreased stability or enzymatic activity for the respective single mutants. The double mutants were assayed for catalysis, inhibition, and stability. Crystal structures were analyzed for the double mutants at resolutions of 2.2-1.2 A to determine the associated molecular changes. Sequence-dependent changes in protease-inhibitor interactions were observed in the crystal structures. Mutations D30N, K45I, and V82S showed altered interactions with inhibitor residues at P2/P2', P3/P3'/P4/P4', and P1/P1', respectively. One of the conformations of Met90 in K45I/L90M has an unfavorably close contact with the carbonyl oxygen of Asp25, as observed previously in the L90M single mutant. The observed catalytic efficiency and inhibition for the double mutants depended on the specific substrate or inhibitor. In particular, large variation in cleavage of p6(pol)-PR substrate was observed, which is likely to result in defects in the maturation of the protease from the Gag-Pol precursor and hence viral replication. Three of the double mutants showed values for stability that were intermediate between the values observed for the respective single mutants. D30N/V82S mutant showed lower stability than either of the two individual mutations, which is possibly due to concerted changes in the central P2-P2' and S2-S2' sites. The complex effects of combining mutations are discussed.
PDB ID: 1K2BDownload
MMDB ID: 103672
PDB Deposition Date: 2001/9/26
Updated in MMDB: 2012/10
Experimental Method:
x-ray diffraction
Resolution: 1.7  Å
Source Organism:
Similar Structures:
Biological Unit for 1K2B: dimeric; determined by author and by software (PISA)
Molecular Components in 1K2B
Label Count Molecule
Proteins (2 molecules)
Protease Retropepsin
Molecule annotation
Chemical (1 molecule)
* Click molecule labels to explore molecular sequence information.

Citing MMDB