Folded monomer of HIV-1 protease

Area of Science:

• Biochemistry
• Structural Biology
• Virology

Background:

• Human immunodeficiency virus type 1 protease (HIV-1 protease) is essential for viral maturation and replication.
• The active protease exists as a stable dimer, formed through an intricate interplay of folding and dimerization.
• Drug resistance necessitates the development of novel protease inhibitors.

Purpose of the Study:

• To investigate the structural and functional consequences of a specific mutation (R87K) in HIV-1 protease.
• To identify key regions critical for protease dimerization and stability.
• To inform the rational design of new HIV-1 protease inhibitors.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• Sedimentation equilibrium studies
• Analysis of mutant proteases with terminal region deletions

Main Results:

• The R87K mutant protease forms a stable monomer with a fold similar to a single subunit of the wild-type dimer.
• Inhibitor binding to the R87K mutant induces stable dimer formation.
• The inner C-terminal beta-sheet (residues 96-99) is essential for HIV-1 protease dimer formation, while N-terminal beta-strands contribute to dimer stability.

Conclusions:

• Loss of interactions involving Arg(87) destabilizes the protease monomer by perturbing the inner C-terminal beta-sheet.
• The inner C-terminal beta-strands are indispensable for dimerization.
• Understanding monomer fold and dimerization regions can guide the design of new inhibitors to combat drug resistance.