Stabilization of HIV proteinase dimer by bound substrate.
Upon the binding of a synthetic nonapeptide substrate, the catalytically active dimeric form of HIV proteinase is strongly stabilized against dissociation into inactive subunits. The dissociation of the ternary Michaelis complex into protein monomers is immeasurably low (apparent dissociation constant in the picomolar range), while the dimer-to-monomer equilibrium dissociation constant at pH 4.7 and at ionic strength 1.0 M is 30.4 +/- 1.6 nM. Consequently, the apparent activity of HIV proteinase depends on the order in which the enzyme and the substrate are added to in vitro assays. Substrate-induced stabilization should be carefully considered in designing kinetic studies of all dissociative retroviral enzymes, the proteinase, the integrase, and the reverse transcriptase.
Kuzmic
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P
School of Pharmacy, University of Wisconsin, Madison 53706.
García-Echeverría
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C
Rich
D H
DH
D000595:Amino Acid Sequence; D004795:Enzyme Stability; D016333:HIV Protease / Q000737:chemistry* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D046911:Macromolecular Substances; D008433:Mathematics; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D009994:Osmolar Concentration; D011485:Protein Binding; D016339:Spectrometry, Mass, Fast Atom Bombardment
D046911:Macromolecular Substances; D009842:Oligopeptides; D016333:HIV Protease