1
|
Bourque JR, Bearne SL. Mutational analysis of the active site flap (20s loop) of mandelate racemase. Biochemistry 2007; 47:566-78. [PMID: 18092808 DOI: 10.1021/bi7015525] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mandelate racemase from Pseudomonas putida catalyzes the Mg2+-dependent 1,1-proton transfer that interconverts the enantiomers of mandelate. Residues of the 20s and 50s loops determine, in part, the topology and polarity of the active site and hence the substrate specificity. Previously, we proposed that, during racemization, the phenyl ring of mandelate moves between an S-pocket comprised of residues from the 50s loop and an R-pocket comprised of residues from the 20s loop [Siddiqi, F., Bourque, J. R., Jiang, H., Gardner, M., St. Maurice, M., Blouin, C., and Bearne, S. L. (2005) Biochemistry 44, 9013-9021]. The 20s loop constitutes a mobile beta-meander flap that covers the active site cavity shielding it from solvent and controlling entry and egress of ligands. To understand the role of the 20s loop in catalysis and substrate specificity, we constructed a series of mutants (V22A, V22I, V22F, T24S, A25V, V26A, V26L, V26F, V29A, V29L, V29F, V26A/V29L, and V22I/V29L) in which the sizes of hydrophobic side chains of the loop residues were varied. Catalytic efficiencies (kcat/Km) for all mutants were reduced between 6- and 40-fold with the exception of those of V22I, V26A, V29L, and V22I/V29L which had near wild-type efficiencies with mandelate. Thr 24 and Ala 25, located at the tip of the 20s loop, were particularly sensitive to minor alterations in the size of their hydrophobic side chains; however, most mutations were tolerated quite well, suggesting that flap mobility could compensate for increases in the steric bulk of hydrophobic side chains. With the exception of V29L, with mandelate as the substrate, and V22F and V26A/V29L, with 2-naphthylglycolate (2-NG) as the substrate, the values of kcat and Km were not altered in a manner consistent with steric obstruction of the R-pocket, perhaps due to flap mobility compensating for the increased size of the hydrophobic side chains. Surprisingly, V22I and V29L catalyzed the racemization of the bulkier substrate 2-NG with kcat/Km values approximately 2-fold greater than those observed for wild-type mandelate racemase. Although minor changes in substrate specificity were achieved through alterations of the active site flap of mandelate racemase, our results suggest that hydrophobic residues that reside on a flexible flap and define the topology of an active site through their van der Waals contacts with the substrate are quite tolerant of a variety of steric substitutions.
Collapse
Affiliation(s)
- Jennifer R Bourque
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 1X5, Canada
| | | |
Collapse
|
2
|
Louis JM, Ishima R, Torchia DA, Weber IT. HIV-1 protease: structure, dynamics, and inhibition. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2007; 55:261-98. [PMID: 17586318 DOI: 10.1016/s1054-3589(07)55008-8] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- John M Louis
- Laboratory of Chemical Physics, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | |
Collapse
|
3
|
Heaslet H, Kutilek V, Morris GM, Lin YC, Elder JH, Torbett BE, Stout CD. Structural insights into the mechanisms of drug resistance in HIV-1 protease NL4-3. J Mol Biol 2005; 356:967-81. [PMID: 16403521 DOI: 10.1016/j.jmb.2005.11.094] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 11/23/2005] [Accepted: 11/30/2005] [Indexed: 11/25/2022]
Abstract
The development of resistance to anti-retroviral drugs targeted against HIV is an increasing clinical problem in the treatment of HIV-1-infected individuals. Many patients develop drug-resistant strains of the virus after treatment with inhibitor cocktails (HAART therapy), which include multiple protease inhibitors. Therefore, it is imperative that we understand the mechanisms by which the viral proteins, in particular HIV-1 protease, develop resistance. We have determined the three-dimensional structure of HIV-1 protease NL4-3 in complex with the potent protease inhibitor TL-3 at 2.0 A resolution. We have also obtained the crystal structures of three mutant forms of NL4-3 protease containing one (V82A), three (V82A, M46I, F53L) and six (V82A, M46I, F53L, V77I, L24I, L63P) point mutations in complex with TL-3. The three protease mutants arose sequentially under ex vivo selective pressure in the presence of TL-3, and exhibit fourfold, 11-fold, and 30-fold resistance to TL-3, respectively. This series of protease crystal structures offers insights into the biochemical and structural mechanisms by which the enzyme can overcome inhibition by TL-3 while recovering some of its native catalytic activity.
Collapse
Affiliation(s)
- Holly Heaslet
- Department of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., La Jolla, CA 92037, USA.
| | | | | | | | | | | | | |
Collapse
|
4
|
Sperka T, Pitlik J, Bagossi P, Tözsér J. Beta-lactam compounds as apparently uncompetitive inhibitors of HIV-1 protease. Bioorg Med Chem Lett 2005; 15:3086-90. [PMID: 15893929 DOI: 10.1016/j.bmcl.2005.04.020] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Revised: 03/31/2005] [Accepted: 04/14/2005] [Indexed: 10/25/2022]
Abstract
Compounds of a combinatorial monocyclic beta-lactam library were found to be apparently uncompetitive inhibitors of HIV-1 protease, providing lead compounds for a new class of HIV protease inhibitors.
Collapse
Affiliation(s)
- Tamás Sperka
- Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, University of Debrecen, Faculty of Medicine, H-4012 Debrecen, Hungary
| | | | | | | |
Collapse
|
5
|
Fehér A, Boross P, Sperka T, Oroszlan S, Tözsér J. Expression of the murine leukemia virus protease in fusion with maltose-binding protein in Escherichia coli. Protein Expr Purif 2004; 35:62-8. [PMID: 15039067 DOI: 10.1016/j.pep.2004.01.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2003] [Revised: 01/12/2004] [Indexed: 01/15/2023]
Abstract
The protease of murine leukemia virus (MLV) was cloned into pMal-c2 vector, expressed in fusion with maltose-binding protein (MBP), and purified to homogeneity after Factor Xa cleavage of the chimeric protein. Substantial degradation of the fusion protein was observed during expression, which severely diminished the yield. The degree of degradation of the fusion protein was even more pronounced when a single-chain form of the MLV protease was cloned after the gene coding for MBP. To increase the yield, a hexahistidine tag with an additional Factor Xa cleavage site was cloned after the protease and nickel chelate affinity chromatography was used as the first purification step. The modified procedure resulted in substantially higher yield as compared to the original procedure. The degradation of hexahistidine-tagged active site mutant MLV protease was very low and comparable to that obtained with hexahistidine-tagged MBP, but purified MLV protease alone was not able to degrade purified MBP, suggesting that during expression the active MLV protease may activate bacterial proteases which appear to be responsible for the degradation of the fusion proteins.
Collapse
Affiliation(s)
- Anita Fehér
- Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary
| | | | | | | | | |
Collapse
|
6
|
Katoh E, Louis JM, Yamazaki T, Gronenborn AM, Torchia DA, Ishima R. A solution NMR study of the binding kinetics and the internal dynamics of an HIV-1 protease-substrate complex. Protein Sci 2003; 12:1376-85. [PMID: 12824484 PMCID: PMC2323926 DOI: 10.1110/ps.0300703] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
NMR studies of the binding of a substrate to an inactive HIV-1 protease construct, containing an active site mutation PR(D25N), are reported. Substrate titration measurements monitored by HSQC spectra and a (15)N-edited NOESY experiment show that the chromogenic substrate analog of the capsid/p2 cleavage site binds to PR(D25N) with an equilibrium dissociation constant, K(D), of 0.27 +/- 0.05 mM, and upper limits of the association and dissociation rate constants, 2 x 10(4) M(-1)s(-1) and 10 s(-1), respectively, at 20 degrees C, pH 5.8. This association rate constant is not in the diffusion limit, suggesting that association is controlled by a rare event, such as opening of the protease flaps. Analysis of (15)N relaxation experiments reveals a slight reduction of S(2) values in the flap region, indicating a small increase in the amplitude of internal motion on the sub-nsec timescale. In addition, several residues in the flap region are mobile on the conformational exchange timescale, msec-microsec. Flap dynamics of the protease-substrate complex are compared with those of protease-inhibitor complexes, and the implications of these results for substrate-binding models are discussed.
Collapse
Affiliation(s)
- Etsuko Katoh
- Biochemistry Department, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan
| | - John M. Louis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Toshimasa Yamazaki
- Biochemistry Department, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8602, Japan
| | - Angela M. Gronenborn
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Dennis A. Torchia
- Molecular Structural Biology Unit, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892-4307, USA
| | - Rieko Ishima
- Molecular Structural Biology Unit, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892-4307, USA
| |
Collapse
|
7
|
Choudhury S, Everitt L, Pettit SC, Kaplan AH. Mutagenesis of the dimer interface residues of tethered and untethered HIV-1 protease result in differential activity and suggest multiple mechanisms of compensation. Virology 2003; 307:204-12. [PMID: 12667791 DOI: 10.1016/s0042-6822(02)00080-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
As is the case for all retroviruses, the protease of HIV-1 is only functional as a homodimer; dimerization of two protease monomers results in the formation of the enzyme active site. This dimer structure is supported primarily by interactions between the first four amino-terminal and the last four carboxy-terminal amino acids. These eight amino acids form a beta-sheet in which hydrophobic residues are oriented towards the core of the molecule and polar residues are directed towards the solvent. Although the structure of the dimer interface has been determined, the forces that support dimerization have not been fully characterized. Here, we describe a tethered construct in which two protease monomers are joined by a 5 amino acid linker. We evaluate the relative role of each dimer interface residue in functional homo- and heterodimers. Our studies indicate that the hydrophobic residues of the dimer interface are particularly important in maintaining enzyme activity and that enzyme activity is more sensitive to substitutions of the C-terminal amino acids. Further, we demonstrate that the presence of the tether is able to compensate for mutations within the dimer interface that inactivate the enzyme.
Collapse
Affiliation(s)
- Sumana Choudhury
- Department of Medicine, UNC School of Medicine, Chapel Hill, NC 27599-7030, USA
| | | | | | | |
Collapse
|
8
|
Abstract
The total synthesis, at will, of a wide variety of protein and enzyme molecules is made feasible by modem chemical ligation methods. As Emil Fischer intuitively understood, synthetic access to the enzyme molecule enables the power of chemical science to be applied to elucidating the molecular basis of catalytic function in unprecedented detail.
Collapse
Affiliation(s)
- Stephen Kent
- Institute for Biophysical Dynamics, Department of Chemistry, The University of Chicago, IL 60637, USA.
| |
Collapse
|
9
|
Louis JM, Weber IT, Tözsér J, Clore GM, Gronenborn AM. HIV-1 protease: maturation, enzyme specificity, and drug resistance. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2001; 49:111-46. [PMID: 11013762 DOI: 10.1016/s1054-3589(00)49025-3] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Affiliation(s)
- J M Louis
- Laboratory of Chemical Physics, National Institute of Diabetes, Bethesda, Maryland 20892-0580, USA
| | | | | | | | | |
Collapse
|
10
|
Tözsér J. Specificity of Retroviral Proteinases Based on Substrates Containing Tyrosine and Proline at the Site of Cleavage. Pathol Oncol Res 2001; 3:142-146. [PMID: 11173643 DOI: 10.1007/bf02907811] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The retroviral proteinase (PR) plays crucial roles in the viral life cycle, therefore it is a target for chemotherapy. However, resistance rapidly develops due to frequent mutations. Studies to determine the common features of the specificity of different retroviral PRs may help to design broad spectrum inhibitors and reduce the possibility of viable mutants. We have studied the specificity of various retroviral proteinases including those the PR of HIV-1, HIV-2, equine infectious anemia virus and avian myeloblastosis virus using oligopeptide substrates. A series of oligopeptides containing substitutions in a sequence Val-Ser-Gln-Asn-Tyr*Pro-Ile-Val-Gln (asterisk indicates the site of cleavage) representing a naturally occurring cleavage site in HIV-1 was used to characterize the seven substrate binding subsites of the enzymes. The unsubstituted substrate is a typical class 1 cleavage site substrate containing an aromatic amino acid and a proline residue at the site of cleavage. The largest differences in kinetics of substrate hydrolysis were obtained with peptides containing substitutions of the Ser and Asn residues. Detailed analysis of the results by molecular modeling and comparison with previously reported data revealed the common characteristics of the specificity of the PRs as well as its strong dependence on the sequence context of the substrate. However, molecular modeling in many cases provided explanation for the sequence context dependence. Also, comparison of the specificity of the enzymes suggests that the specificity of HIV-1 and -2 PRs is rather exceptional preferring hydrophilic residues at the most discriminative positions while other PRs prefer hydrophobic residues.
Collapse
Affiliation(s)
- József Tözsér
- University Medical School of Debrecen, Department of Biochemistry, Debrecen, Hungary
| |
Collapse
|
11
|
Baca M, Kent SB. Protein Backbone Engineering through Total Chemical Synthesis: New Insight into the Mechanism of HIV-1 Protease Catalysis. Tetrahedron 2000. [DOI: 10.1016/s0040-4020(00)00835-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
12
|
Strisovsky K, Tessmer U, Langner J, Konvalinka J, Kräusslich HG. Systematic mutational analysis of the active-site threonine of HIV-1 proteinase: rethinking the "fireman's grip" hypothesis. Protein Sci 2000; 9:1631-41. [PMID: 11045610 PMCID: PMC2144712 DOI: 10.1110/ps.9.9.1631] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Aspartic proteinases share a conserved network of hydrogen bonds (termed "fireman's grip"), which involves the hydroxyl groups of two threonine residues in the active site Asp-Thr-Gly triplets (Thr26 in the case of human immunodeficiency virus type 1 (HIV-1) PR). In the case of retroviral proteinases (PRs), which are active as symmetrical homodimers, these interactions occur at the dimer interface. For a systematic analysis of the "fireman's grip," Thr26 of HIV-1 PR was changed to either Ser, Cys, or Ala. The variant enzymes were tested for cleavage of HIV-1 derived peptide and polyprotein substrates. PR(T26S) and PR(T26C) showed similar or slightly reduced activity compared to wild-type HIV-1 PR, indicating that the sulfhydryl group of cysteine can substitute for the hydroxyl of the conserved threonine in this position. PR(T26A), which lacks the "fireman's grip" interaction, was virtually inactive and was monomeric in solution at conditions where wild-type PR exhibited a monomer-dimer equilibrium. All three mutations had little effect when introduced into only one chain of a linked dimer of HIV-1 PR. In this case, even changing both Thr residues to Ala yielded residual activity suggesting that the "fireman's grip" is not essential for activity but contributes significantly to dimer formation. Taken together, these results indicate that the "fireman's grip" is crucial for stabilization of the retroviral PR dimer and for overall stability of the enzyme.
Collapse
Affiliation(s)
- K Strisovsky
- Department of Biochemistry, Institute of Organic Chemistry and Biochemistry, Czech Academy of Science, Praha, Czech Republic
| | | | | | | | | |
Collapse
|
13
|
Wlodawer A, Gustchina A. Structural and biochemical studies of retroviral proteases. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1477:16-34. [PMID: 10708846 DOI: 10.1016/s0167-4838(99)00267-8] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Retroviral proteases form a unique subclass of the family of aspartic proteases. These homodimeric enzymes from a number of viral sources have by now been extensively characterized, both structurally and biochemically. The importance of such knowledge to the development of new drugs against AIDS has been, to a large extent, the driving force behind this progress. High-resolution structures are now available for enzymes from human immunodeficiency virus types 1 and 2, simian immunodeficiency virus, feline immunodeficiency virus, Rous sarcoma virus, and equine infectious anemia virus. In this review, structural and biochemical data for retroviral proteases are compared in order to analyze the similarities and differences between the enzymes from different sources and to enhance our understanding of their properties.
Collapse
Affiliation(s)
- A Wlodawer
- Macromolecular Crystallography Laboratory, Program in Structural Biology, NCI-Frederick Cancer Research and Development Center, Frederick, MD 21702, USA.
| | | |
Collapse
|
14
|
Ishima R, Freedberg DI, Wang YX, Louis JM, Torchia DA. Flap opening and dimer-interface flexibility in the free and inhibitor-bound HIV protease, and their implications for function. Structure 1999; 7:1047-55. [PMID: 10508781 DOI: 10.1016/s0969-2126(99)80172-5] [Citation(s) in RCA: 225] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND (1)H and (15)N transverse relaxation measurements on perdeuterated proteins are ideally suited for detecting backbone conformational fluctuations on the millisecond-microsecond timescale. The identification of conformational exchange on this timescale by measuring the relaxation of both (1)H and (15)N holds great promise for the elucidation of functionally relevant conformational changes in proteins. RESULTS We measured the transverse (1)H and (15)N relaxation rates of backbone amides of HIV-1 protease in its free and inhibitor-bound forms. An analysis of these rates, obtained as a function of the effective rotating frame field, provided information about the timescale of structural fluctuations in several regions of the protein. The flaps that cover the active site of the inhibitor-bound protein undergo significant changes of backbone (φ,psi) angles, on the 100 micros timescale, in the free protein. In addition, the intermonomer beta-sheet interface of the bound form, which from protease structure studies appears to be rigid, was found to fluctuate on the millisecond timescale. CONCLUSIONS We present a working model of the flap-opening mechanism in free HIV-1 protease which involves a transition from a semi-open to an open conformation that is facilitated by interaction of the Phe53 ring with the substrate. We also identify a surprising fluctuation of the beta-sheet intermonomer interface that suggests a structural requirement for maturation of the protease. Thus, slow conformational fluctuations identified by (1)H and (15)N transverse relaxation measurements can be related to the biological functions of proteins.
Collapse
Affiliation(s)
- R Ishima
- Molecular Structural Biology Unit National Institute of Dental and Craniofacial Research National Institutes of Health Bethesda, MD 20892, USA
| | | | | | | | | |
Collapse
|
15
|
Mahalingam B, Louis JM, Reed CC, Adomat JM, Krouse J, Wang YF, Harrison RW, Weber IT. Structural and kinetic analysis of drug resistant mutants of HIV-1 protease. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 263:238-45. [PMID: 10429209 DOI: 10.1046/j.1432-1327.1999.00514.x] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mutants of HIV-1 protease that are commonly selected on exposure to different drugs, V82S, G48V, N88D and L90M, showed reduced catalytic activity compared to the wild-type protease on cleavage site peptides, CA-p2, p6pol-PR and PR-RT, critical for viral maturation. Mutant V82S is the least active (2-20% of wild-type protease), mutants N88D, R8Q, and L90M exhibit activities ranging from 20 to 40% and G48V from 50 to 80% of the wild-type activity. In contrast, D30N is variable in its activity on different substrates (10-110% of wild-type), with the PR-RT site being the most affected. Mutants K45I and M46L, usually selected in combination with other mutations, showed activities that are similar to (60-110%) or greater than (110-530%) wild-type, respectively. No direct relationship was observed between catalytic activity, inhibition, and structural stability. The mutants D30N and V82S were similar to wild-type protease in their stability toward urea denaturation, while R8Q, G48V, and L90M showed 1.5 to 2.7-fold decreased stability, and N88D and K45I showed 1.6 to 1.7-fold increased stability. The crystal structures of R8Q, K45I and L90M mutants complexed with a CA-p2 analog inhibitor were determined at 2.0, 1.55 and 1.88 A resolution, respectively, and compared to the wild-type structure. The intersubunit hydrophobic contacts observed in the crystal structures are in good agreement with the relative structural stability of the mutant proteases. All these results suggest that viral resistance does not arise by a single mechanism.
Collapse
Affiliation(s)
- B Mahalingam
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, USA
| | | | | | | | | | | | | | | |
Collapse
|
16
|
Vandamme AM, Van Laethem K, De Clercq E. Managing resistance to anti-HIV drugs: an important consideration for effective disease management. Drugs 1999; 57:337-61. [PMID: 10193687 DOI: 10.2165/00003495-199957030-00006] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Current recommendations for the treatment of HIV-infected patients advise highly active antiretroviral therapy (HAART) consisting of combinations of 3 or more drugs to provide long-term clinical benefit. This is because only a complete suppression of virus replication will be able to prevent virus drug resistance, the main cause of drug failure. Virus drug resistance may remain a cause of concern in patients who have already received suboptimal mono- or bitherapy, or for patients who do not experience complete shut-down of virus replication under HAART. For these patients, replacement of one combination therapy regimen by another at drug failure, taking into account the existing resistance profile, will be needed. The development of new drugs will remain necessary for those patients who have failed to respond to all currently available drugs, as will be the institution of more effective and less toxic HAART regimens.
Collapse
Affiliation(s)
- A M Vandamme
- Rega Institute for Medical Research and University Hospitals, Katholieke Universiteit Leuven, Belgium.
| | | | | |
Collapse
|
17
|
Vandamme AM, Van Vaerenbergh K, De Clercq E. Anti-human immunodeficiency virus drug combination strategies. Antivir Chem Chemother 1998; 9:187-203. [PMID: 9875399 DOI: 10.1177/095632029800900301] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
It is now generally accepted that mono- and bitherapy for human immunodeficiency virus type 1 (HIV-1) infection are only transiently efficient mainly due to virus drug resistance. To obtain a sustained benefit from antiviral therapy, current guidelines recommend at least triple-drug combinations, or the so-called highly active antiretroviral therapy (HAART). In some patients, HAART can be problematic, either because it is difficult to remain compliant or because previous suboptimum therapies have limited the choice of drugs. For compliant drug-naive patients, HAART should be able to offer long-term virus suppression, when changing from first- to second- to third-line HAART at drug failure. Long-term treatment might ultimately result in multi-drug resistant virus leaving few options for salvage therapy. HIV drug resistance testing to guide this salvage therapy and the development of new drugs to allow new options will therefore remain priorities in anti-HIV drug research.
Collapse
Affiliation(s)
- A M Vandamme
- Rega Institute for Medical Research, Katholieke Universiteit Leuven, Belgium.
| | | | | |
Collapse
|
18
|
Wu J, Adomat JM, Ridky TW, Louis JM, Leis J, Harrison RW, Weber IT. Structural basis for specificity of retroviral proteases. Biochemistry 1998; 37:4518-26. [PMID: 9521772 DOI: 10.1021/bi972183g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The Rous sarcoma virus (RSV) protease S9 variant has been engineered to exhibit high affinity for HIV-1 protease substrates and inhibitors in order to verify the residues deduced to be critical for the specificity differences. The variant has 9 substitutions (S38T, I42D, I44V, M73V, A100L, V104T, R105P, G106V, and S107N) of structurally equivalent residues from HIV-1 protease. Unlike the wild-type enzyme, RSV S9 protease hydrolyzes peptides representing the HIV-1 protease polyprotein cleavage sites. The crystal structure of RSV S9 protease with the inhibitor, Arg-Val-Leu-r-Phe-Glu-Ala-Nle-NH2, a reduced peptide analogue of the HIV-1 CA-p2 cleavage site, has been refined to an R factor of 0.175 at 2.4-A resolution. The structure shows flap residues that were not visible in the previous crystal structure of unliganded wild-type enzyme. Flap residues 64-76 are structurally similar to residues 47-59 of HIV-1 protease. However, residues 61-63 form unique loops at the base of the flaps. Mutational analysis indicates that these loop residues are essential for catalytic activity. Side chains of flap residues His 65 and Gln 63' make hydrogen bond interactions with the inhibitor P3 amide and P4' carbonyl oxygen, respectively. Other interactions of RSV S9 protease with the CA-p2 analogue are very similar to those observed in the crystal structure of HIV-1 protease with the same inhibitor. This is the first crystal structure of an avian retroviral protease in complex with an inhibitor, and it verifies our knowledge of the molecular basis for specificity differences between RSV and HIV-1 proteases.
Collapse
Affiliation(s)
- J Wu
- Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
| | | | | | | | | | | | | |
Collapse
|