Visualizing transient events in amino-terminal autoprocessing of HIV-1 protease

Nature. 2008 Oct 2;455(7213):693-6. doi: 10.1038/nature07342.


HIV-1 protease processes the Gag and Gag-Pol polyproteins into mature structural and functional proteins, including itself, and is therefore indispensable for viral maturation. The mature protease is active only as a dimer with each subunit contributing catalytic residues. The full-length transframe region protease precursor appears to be monomeric yet undergoes maturation via intramolecular cleavage of a putative precursor dimer, concomitant with the appearance of mature-like catalytic activity. How such intramolecular cleavage can occur when the amino and carboxy termini of the mature protease are part of an intersubunit beta-sheet located distal from the active site is unclear. Here we visualize the early events in N-terminal autoprocessing using an inactive mini-precursor with a four-residue N-terminal extension that mimics the transframe region protease precursor. Using paramagnetic relaxation enhancement, a technique that is exquisitely sensitive to the presence of minor species, we show that the mini-precursor forms highly transient, lowly populated (3-5%) dimeric encounter complexes that involve the mature dimer interface but occupy a wide range of subunit orientations relative to the mature dimer. Furthermore, the occupancy of the mature dimer configuration constitutes a very small fraction of the self-associated species (accounting for the very low enzymatic activity of the protease precursor), and the N-terminal extension makes transient intra- and intersubunit contacts with the substrate binding site and is therefore available for autocleavage when the correct dimer orientation is sampled within the encounter complex ensemble.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Dimerization
  • HIV Protease / chemistry*
  • HIV Protease / genetics
  • HIV Protease / metabolism*
  • HIV-1 / enzymology*
  • HIV-1 / genetics
  • Models, Molecular
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Precursors / chemistry*
  • Protein Precursors / genetics
  • Protein Precursors / metabolism*
  • Protein Processing, Post-Translational*
  • Protein Structure, Tertiary
  • Spin Labels
  • gag Gene Products, Human Immunodeficiency Virus / chemistry
  • gag Gene Products, Human Immunodeficiency Virus / metabolism


  • Protein Precursors
  • Spin Labels
  • gag Gene Products, Human Immunodeficiency Virus
  • HIV Protease
  • p16 protease, Human immunodeficiency virus 1