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The X-ray structure of a complex of HIV-1 protease (PR) with a phenylnorstatine inhibitor Z-Pns-Phe-Glu-Glu-NH2 has been determined at 1.03 Å, the highest resolution so far reported for any HIV PR complex. The inhibitor shows subnanomolar Ki values for both the wild-type PR and the variant representing one of the most common mutations linked to resistance development. The structure comprising the phenylnorstatine moiety of (2R,3S)-chirality displays a unique pattern of hydrogen bonding to the two catalytic aspartate residues. This high resolution makes it possible to assess the donor and acceptor relations of this hydrogen bonding and to indicate a proton shared by the two catalytic residues. A structural mechanism for the unimpaired inhibition of the protease Val82Ala mutant is also suggested, based on energy calculations and analyses.

The protease of HIV plays a critical role in the maturation of the infectious particles of the virus. The enzyme has therefore been extensively studied with the objective of developing therapeutics that inhibit viral proliferation. We have produced monoclonal antibodies specific for the HIV‐1 protease, and selected those that inhibit enzyme function for use as probes to study the enzyme's activity and as an eventual aid for the development of potential inhibitors targeted to regions other than the active site. We have characterized two such mAbs, F11.2.32 and 1696, which have inhibition constants in the low nanomolar range and which recognize epitopes from different regions of the protease. The crystal structures of the two antibodies, both in the free state as well as complexes with peptide fragments corresponding to their respective epitopes, have been solved. The structural analyses, taken together with other functional data on the antibodies, suggest mechanisms of protease inhibition by these antibodies. Copyright © 2002 John Wiley & Sons, Ltd.

A complex structure of HIV-1 protease with a hydroxyethylamine-containing inhibitor Boc-Phe-Ψ[(S)-CH(OH)CH2NH]-Phe-Gln-Phe-NH2 has been determined by X-ray diffraction to 1.8 Å resolution. The inhibitor is bound in the active site of the protease dimer with its hydroxyethylamine isostere participating in hydrogen bonds to the catalytic aspartates 25 and 25‘ and glycine 27‘ of the active site triads via five hydrogen bonds. The isostere amine interactions with the catalytic aspartates result in a displacement of the isostere hydroxy group in comparison with the common position known for analogous hydroxyethylamine containing inhibitors. A comparison with another inhibitor of this series shows that the change of one atom of the P2‘ side chain (Glu/Gln) leads to an altered ability of creating hydrogen bonds to the active site and within the inhibitor molecule. The diffraction data collected at a synchrotron radiation source enabled a detailed analysis of the complex solvation and of alternative conformations of protein side chains.