PEDS Advance Access published online on May 13, 2008
Protein Engineering Design and Selection, doi:10.1093/protein/gzn022
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Novel macromolecular inhibitors of human immunodeficiency virus-1 protease
1Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, PO Box 6, Debrecen H-4012, Hungary 2Department of Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15260 3Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0520, USA
4 To whom correspondence should be addressed. E-mail: peter{at}indi.biochem.dote.hu
An intracellularly expressed defective human immunodeficiency virus type-1 (HIV-1) protease (PR) monomer could function as a dominant-negative inhibitor of the enzyme that requires dimerization for activity. Based on in silico studies, two mutant PRs harboring hydrophilic mutations, capable of forming favorable inter- and intra-subunit interactions, were selected: PRRE containing Asp25Arg and Gly49Glu mutations, and PRRER containing an additional Ile50Arg mutation. The mutants were expressed and tested by PR assays, nuclear magnetic resonance (NMR) and cell culture experiments. The mutant PRs showed dose-dependent inhibition of the wild-type PR in a fluorescent microtiter plate PR assay. Furthermore, both mutants were retained by hexahistidine-tagged wild-type HIV-1 PR immobilized on nickel-chelate affinity resin. For the first time, heterodimerization between wild-type and dominant-negative mutant PRs were also demonstrated by NMR spectroscopy. 1H–15N Heteronuclear Single Quantum Coherence NMR spectra showed that although PRRE has a high tendency to aggregate, PRRER exists mainly as a folded monomer at 25–35 µM concentration, but in the presence of wild-type PR in a ratio of 1:1, heterodimerization occurs with both mutants. While the recombinant virus containing the PRRE sequence showed only very low level of expression, expression of the viral proteins of the virus with the PRRER sequence was comparable with that of the wild-type. In cell culture experiments, infectivity of viral particles containing PRRER protein was reduced by 82%, at mutant to wild-type infective DNA ratio of 2:1.
Keywords: dimerization/human immunodeficiency virus-1 protease/macromolecular inhibitor/NMR/trans-dominant effect
Received January 11, 2008; revised March 28, 2008; accepted March 31, 2008.