- Open Access
Two M-T hook residues greatly improve the antiviral activity and resistance profile of the HIV-1 fusion inhibitor SC29EK
- Huihui Chong†1,
- Zonglin Qiu†1,
- Jianping Sun†1,
- Yuanyuan Qiao1,
- Xingxing Li1 and
- Yuxian He1Email author
© Chong et al.; licensee BioMed Central Ltd. 2014
- Received: 1 March 2014
- Accepted: 17 April 2014
- Published: 27 May 2014
Peptides derived from the C-terminal heptad repeat (CHR) of HIV-1 gp41 such as T20 (Enfuvirtide) and C34 are potent viral fusion inhibitors. We have recently found that two N-terminal residues (Met115 and Thr116) of CHR peptides form a unique M-T hook structure that can greatly enhance the binding and anti-HIV activity of inhibitors. Here, we applied two M-T hook residues to optimize SC29EK, an electrostatically constrained peptide inhibitor with a potent anti-HIV activity.
The resulting peptide MT-SC29EK showed a dramatically increased binding affinity and could block the six-helical bundle (6-HB) formation more efficiently. As expected, MT-SC29EK potently inhibited HIV-1 entry and infection, especially against those T20- and SC29EK-resistant HIV-1 variants. More importantly, MT-SC29EK and its short form (MT-SC22EK) suffered from the difficulty to induce HIV-1 resistance during the in vitro selection, suggesting their high genetic barriers to the development of resistance.
Our studies have verified the M-T hook structure as a vital strategy to design novel HIV-1 fusion inhibitors and offered an ideal candidate for clinical development.
- Fusion inhibitor
- M-T hook structure
The crystal structure of 6-HB core reveals a deep hydrophobic pocket on the C-terminal portion of NHR trimer, which is inserted by three hydrophobic residues from the pocket-binding domain (PBD) of CHR [12–14]. It is believed that the pocket critically determines the stability of NHR-CHR interaction and can serve as an ideal target for inhibitors [15, 16]. Due to the lack of the pocket-binding sites by T20, the CHR-derived peptide C34 has been widely used as a template for peptide engineering [17–19]. As a key strategy, the salt-bridge structures were introduced into C34 sequence creating the electrostatically constrained peptides such as SC34EK , T2635  and Sifuvirtide (SFT) , in which the amino acids at the solvent-accessible sites of helical bundle were replaced with glutamate (E) and lysine (K) and those at the NHR-interactive sites were maintained, thus in an α-helical heptad repeat residues separated by three positions (i versus i + 4) were closely positioned in space on the same site of the helix (Figure 1). As compared to C34, these electrostatically-engineered inhibitors possessed the significantly improved anti-HIV profiles [20–22]. By truncating the C-terminus of SC34EK, the relatively short peptide SC29EK was generated with a comparable anti-HIV activity but its further truncation (SC22EK) could not be tolerated . Recently, we discovered that two residues (Met115 and Thr116) preceding the pocket-binding domain of CHR peptides adopt a unique M-T hook structure that can greatly enhance the pocket-binding . Indeed, the M-T hook structure-modified C34 and SC22EK exhibited the dramatically increased binding affinity and antiviral activity [24, 25], suggesting a totally new strategy for designing or optimizing HIV-1 fusion inhibitors. In this study, we applied two hook residues to modify SC29EK and observed a significant optimization. Importantly, the resulting peptide MT-SC29EK showed a highly improved potency to inhibit T20- and SC29EK-resistant HIV-1 variants and a higher genetic barrier to resistance. Our studies have validated a general feature of the M-T hook structure for designing HIV-1 fusion inhibitors and offered a promising candidate for future development.
The M-T hook residues dramatically enhance the stability of 6-HB core
High-affinity interactions of MT-SC29EK with the NHR target
The M-T hook residues markedly increase the potency of SC29EK to block 6-HB
The M-T hook residues significantly improve the antiviral activity of SC29EK
Anti-HIV activity of MT-SC29EK and control peptides a
73.2 ± 9.1
48.6 ± 1.2
2.7 ± 0.1
1.3 ± 0.2
2.6 ± 0.1
1.5 ± 0.1
1.8 ± 0.2
1.0 ± 0.2
1.4 ± 0.2
1.2 ± 0.2
1.1 ± 0.1
0.4 + 0.2
51.3 + 5.4
58.2 + 15.2
2.1 ± 0.2
1.1 ± 0.1
2.2 ± 0.3
0.9 ± 0.2
0.7 ± 0.0
0.2 ± 0.0
Potent activity of MT-SC29EK against T20- and SC29EK-resistant HIV-1 variants
Inhibitory activity of SC29EK and MT-SC29EK against T20-resistant HIV-1 variants a
52.1 ± 8.5
1.8 ± 0.2
0.6 ± 0.1
552.2 ± 123.4
15.0 ± 0.3
0.8 ± 0.2
1842.6 ± 56.1
16.2 ± 1.9
0.6 ± 0.1
378.3 ± 41.7
15.1 ± 1.8
1.7 ± 0.0
1321.5 ± 92.3
83.8 ± 10.8
0.8 ± 0.1
366.8 ± 47.4
7.2 ± 0.2
202.6 ± 12.6
11.7 ± 0.7
1.2 ± 0.0
21.2 ± 4.4
37.7 ± 6.4
0.6 ± 0.0
High-affinity binding of MT-SC29EK to the NHR mutants
MT-SC29EK displays a high genetic barrier to the development of resistance
Previously, we identified that the heptad amino acid motif (110QIWNNMT116) preceding the pocket-binding domain of CHR-derived peptides could dramatically enhance the binding affinity and antiviral activity of inhibitors . Based on the QIWNNMT motif-containing peptide CP621-652, we developed a potent HIV-1 fusion inhibitor named CP32M . However, we did not know the molecular determinants underlying the stability and anti-HIV activity of inhibitors in detail. Recently, we solved the high-resolution crystal structure of CP621-652 complexed by a NHR-derived peptide (T21) . Surprisingly, we found the M-T hook structure, in which the residue Thr116 redirects the peptide chain to position Met115 above the left side of the hydrophobic pocket on the NHR trimer and the side chain of Met115 caps the hydrophobic pocket to stabilize the interaction between the pocket and the pocket-binding domain . To directly define the structure and function of the M-T hook, we generated the peptide MT-C34 by incorporating Met115 and Thr116 into the N-terminus of C34 . The high resolution crystal structure of MT-C34 verified a universal structural feature for CHR-based inhibitors. We also demonstrated that addition of two hook residues could dramatically enhance the binding affinity and thermal stability of 6-HB core. Compared with C34, MT-C34 exhibited the significantly increased activity to inhibit HIV-1 fusion and replication . These findings prompted us to propose a new strategy for designing HIV-1 fusion inhibitors. Very recently, we verified this concept by introducing the M-T hook structure into several CHR-derived short peptides and observed a significant optimization . In the present study, we selected SC29EK as a template to validate the general role of the M-T hook structure, as this electrostatically constrained helical peptide has a relatively short sequence but possesses a potent antiviral activity thus having potential to be further developed for clinical use .
The initial structural data of gp41 6-HBs informed the mechanisms of HIV-1 fusion and its inhibition [12–14]. The CHR-derived peptides act by competitive binding to the exposed NHR during its conformational change to the fusogenic state (i.e. pre-hairpin conformation) and thus block the 6-HB formation in a dominant-negative fashion [16, 17]. It is generally thought that a high-affinity binding is required for an exogenous peptide to compete off the viral CHR thus critically determining the antiviral activity, thereby a number of strategies have been explored to improve the binding affinity of inhibitors [11, 17–19, 30]. Our series of studies have provided a new approach that can dramatically enhance the binding of inhibitors to the NHR target [23–25, 28, 29]. The biophysical data presented here indicated that the binding stability of MT-SC29EK could be greatly increased as compared to that of SC29EK. It is conceivable that two M-T hook residues may integrate the pocket-binding domain thus synergistically enhancing the interactions of MT-SC29EK with the targeting NHR region. Consistent to this hypothesis, MT-SC29EK could physically block the 6-HB formation more efficiently and possessed higher anti-HIV activity. Promisingly, MT-SC29EK showed the most potent inhibition against HIV-1 entry and replication as compared to the well-characterized first- (T20, C34) and next- (T1249, SFT, T2635) generations of HIV-1 inhibitors.
Like other classes of anti-HIV drugs, HIV-1 fusion inhibitors are also facing the problem of drug-resistance. The emergence and spread of T20-resistant HIV-1 strains have already resulted in increased number of patients failing to treatment. T20-resistance has been predominantly mapped to the substitutions in the amino acid 36–45 of the NHR, with a contiguous three residues (G36-I37-V38) being a hotspot [8–10, 31, 32]. Similar to SC34EK and SC29EK, Sifuvirtide (SFT) was also designed by introducing multiple salt-bridges into C34 . Due to its potent anti-HIV activity, SFT has already been advanced into Phase III clinical trials in China and may become the second HIV-1 fusion inhibitor for clinical use. However, SFT could easily induce drug-resistance in the in vitro selection and HIV-1 variants displayed high cross-resistance to T20 . The in vitro selection and resistant profiles of SC34EK and T2635 were also reported [34, 35]. Eggink et al. described four mechanisms of drug resistance: reduced contact, steric obstruction, electrostatic repulsion, and electrostatic attraction. From SFT-resistance, we deduced several additional mechanisms, such as hydrogen bond disruption and hydrophobic contact disruption [33, 37]. Therefore, an ideal next-generation HIV-1 fusion inhibitor should efficiently inhibit the existing inhibitor-resistant HIV-1 variants but itself possessing a high genetic barrier to overcome drug-resistance. Our studies suggested that the M-T hook structure might confer the inhibitors these two features. First, MT-SC29EK was able to potently inhibit a panel of major T20-resistant HIV-1 variants, which also displayed high-level cross-resistance to SC29EK. More impressively, MT-SC29EK and its short version MT-SC22EK suffered from the difficulty of inducing drug-resistance during the in vitro selection, implying their considerable higher genetic barriers than SC29EK or SC22EK to the development of resistance. Very recently, we have found that the M-T hook-modified C34 (MT-C34) and Sifuvirtide (MT-SFT) behaved with a similar phenotype (unpublished data). Taken together, we consider that the M-T hook structure can render the peptide fusion inhibitors with a high genetic barrier to select the resistant HIV-1 variants, which provides an important feature for drug development. It is well established that the residues involving interactions in the NHR pocket are highly conserved during HIV-1 evolution; the mutations of these residues are often lethal to the virus. Thus, the balance between virus survival and drug resistance becomes hard to maintain, and the genetic barrier for drug resistance against the M-T hook should increase [2, 15]. Furthermore, it has been shown that if the drug-target affinity is too high, the virus does not escape by mutating the binding site, but by reducing the window of opportunity for the drug to act [19, 21, 35]. Definitely, more follow-up studies are required to explore how the M-T hook structure can dramatically increase the potency of inhibitors against the known resistant HIV-1 variants and simultaneously confer a high genetic barrier to resistance. Besides selecting the escape viruses and mapping the responsible mutations, the mechanism of action by the M-T hook structure-modified inhibitors should be pursued in the context of the recently solved Env trimer structure [38–40].
We demonstrated that two M-T hook residues have greatly improved the antiviral profiles of SC29EK, verifying the M-T hook structure as a general strategy for designing or optimizing HIV-1 fusion inhibitor. The resulting inhibitor MT-SC29EK has potent inhibitory activity against diverse HIV-1 strains and possesses a high genetic barrier to resistance, thus offering a promising candidate for drug development.
A panel of CHR peptides including T20, C34, SFT, CP32M, T1249, T2635, SC29EK, MT-SC29EK, SC22EK, MT-SC22EK and the NHR peptide N36 and its mutants (I37T, V38A, Q40H, N43K, I37T/N43K, and V38A/N42T) were synthesized by a standard solid-phase FMOC method as described previously . All peptides were acetylated at the N-terminus and amidated at the C-terminus and purified by reversed-phase high-performance liquid chromatography (HPLC). They were verified for purity >95% and correct amino acid composition by mass spectrometry. Concentrations of the peptides were determined by UV absorbance and a theoretically calculated molar-extinction coefficient ϵ (280 nm) of 5500 M-1 · cm-1 and 1490 M-1 · cm-1 based on the number of tryptophan and tyrosine residues, respectively .
Circular dichroism (CD) spectroscopy
CD spectroscopy was performed according to our protocols described previously . Briefly, a CHR peptide (C34, SC29EK or MT-SC29EK) was incubated with an equal molar concentration of N36 or its mutant (I37T, V38A, Q40H, N43K, I37T/N43K, and V38A/N42T) at 37°C for 30 min. The final concentration of each peptide was 10 μM in PBS buffer (pH 7.2). The CD spectra were acquired on a Jasco spectropolarimeter (model J-815) using a 1 nm bandwidth with a 1 nm step resolution from 195 to 260 nm at room temperature. The spectra were corrected by subtraction of a blank corresponding to the solvent. Data were averaged over three accumulations. The α-helical content was calculated from the CD signal by dividing the mean residue ellipticity [θ] at 222 nm by the value expected for 100% helix formation (-33,000 degrees.cm2.dmol-1). The thermal denaturation experiment was performed by monitoring the change in ellipticity [θ] at 222 nm at the increasing temperature (20–98°C) using temperature controller. The temperature was increased at a rate of 1.2°C per min; data were acquired at a 1 nm bandwidth at 222 nm at a frequency of 0.25 Hz. The melting curve was smoothened, and the midpoint of the thermal unfolding transition (Tm) values were taken as the maximum of the derivative d [θ]222/dT. The Tm value was detected at a peptide concentration of 10 μM in PBS buffer.
Isothermal Titration Calorimetry (ITC)
ITC assay was performed using an ITC200 Microcalorimeter instrument (MicroCal, USA) as described previously . In brief, 1 mM N36 dissolved in ddH20 was injected into the chamber containing 100 μM SC29EK or MT-SC29EK. The experiments were carried out at 25°C. The time between injections was 240 s and the stirring speed was 500 rpm. The heats of dilution were determined in control experiments by injecting N36 into ddH20 and subtracted from the heats produced in the corresponding peptide-peptide binding experiments. Data acquisition and analysis were performed using MicroCal Origin software (version 7.0).
Inhibition of 6-HB formation by peptides
The 6-HB core-specific monoclonal antibody NC-1 was obtained from Dr. Shibo Jiang in the New York Blood Center (New York, NY) through the ARRRP, Division of AIDS, NIAID, National Institute of Health. The inhibitory activity of SC29EK or MT-SC29EK on the 6-HB formation was measured by a modified ELISA as previously described . Briefly, a 96-well polystyrene plate was coated with 2 μg/ml NC-1 in 0.1 M Tris buffer (pH 8.8). A tested peptide at graded concentrations was mixed with the biotinylated-C34 (0.1 μM) and incubated with N36 (0.1 μM) at room temperature for 30 min. The mixture was then added to the NC-1-coated plate, followed by incubation for 30 min and washing with a washing buffer (PBS containing 0.1% Tween 20) three times. Then horseradish peroxidase (HRP)-labeled streptavidin (Invitrogen) and the substrate 3,3,5,5- tetramethylbenzidine (Sigma) were sequentially added. Absorbance at 450 nm (A450) was measured using an ELISA reader.
Measurement of anti-HIV activity of peptides
The inhibition of peptides on the HIV-1 entry was determined by single-cycle infection assay as described previously . Briefly, HIV-1 pseudovirus was generated by cotransfecting 293 T cells with an Env-expressing plasmid and a backbone plasmid pSG3Δenv that encodes Env-defective, luciferase-expressing HIV-1 genome. The supernatants were harvested and filtered 48 h after transfection and 50% tissue culture infectious dose (TCID50) was determined in TZM-bl cells. The peptides were prepared with 3-fold dilutions and mixed with 100 TCID50 viruses and then incubated 1 h at room temperature. The mixture was added to TZM-bl cells (104/well) and incubated 48 h at 37°C. The luciferase activity was measured using luciferase assay reagents and a Luminescence Counter (Promega).
The inhibition of peptides on HIV-1 replication was determined by a molecular cloned wild-type HIV-1NL4–3. In brief, the virus stock was harvested and quantified 48 h post-transfection. 100 TCID50 viruses were used to infect TZM-bl cells in the presence or absence of serially diluted peptides. Two days post-infection, the cells were harvested and lysed in reporter lysis buffer and the luciferase activity was measured as described above.
Induction of HIV-1 resistance to inhibitors
The in vitro selection of HIV-1 resistance to peptide inhibitors was performed as described previously . Briefly, MT-4 cells were seeded at 1 × 104 in RPMI 1640 medium containing 10% fetal bovine serum on 12-well plates. The molecular clone of HIV-1NL4–3 was used to infect the cells in the presence or absence of diluted peptide inhibitors (SC29EK, MT-SC29EK, SC22EK and MT-SC22EK). The cells were incubated at 37°C with 5% CO2 until an extensive cytopathic effect was observed. The culture supernatants were harvested and used for next passage on fresh MT-4 cells with 1.5-2 fold increasing concentrations of peptide. Cells and supernatant were harvested at regular time points and stored at -80°C.
This work was supported by grants from the National Science Foundation of China (81025009, 81271830) and National 973 Program of China (2010CB530100). The funding agencies had no role in the study design, data collection and analysis, the decision to publish, or preparation of the manuscript.
- Engelman A, Cherepanov P: The structural biology of HIV-1: mechanistic and therapeutic insights. Nat Rev Microbiol. 2012, 10: 279-290. 10.1038/nrmicro2747.PubMed CentralView ArticlePubMedGoogle Scholar
- Eckert DM, Malashkevich VN, Hong LH, Carr PA, Kim PS: Inhibiting HIV-1 entry: discovery of D-peptide inhibitors that target the gp41 coiled-coil pocket. Cell. 1999, 99: 103-115. 10.1016/S0092-8674(00)80066-5.View ArticlePubMedGoogle Scholar
- Gulick RM, Lalezari J, Goodrich J, Clumeck N, De Jesus E, Horban A, Nadler J, Clotet B, Karlsson A, Wohlfeiler M, Montana JB, McHale M, Sullivan J, Ridgway C, Felstead S, Dunne MW, van der Ryst E, Mayer H, Motivate Study Teams: Maraviroc for previously treated patients with R5 HIV-1 infection. N Engl J Med. 2008, 359: 1429-1441. 10.1056/NEJMoa0803152.PubMed CentralView ArticlePubMedGoogle Scholar
- Fatkenheuer G, Nelson M, Lazzarin A, Konourina I, Hoepelman AI, Lampiris H, Hirschel B, Tebas P, Raffi F, Trottier B, Bellos N, Saag M, Cooper DA, Westby M, Tawadrous M, Sullivan JF, Ridgway C, Dunne MW, Felstead S, Mayer H, van der Ryst E, Motivate Study Teams: Subgroup analyses of maraviroc in previously treated R5 HIV-1 infection. N Engl J Med. 2008, 359: 1442-1455. 10.1056/NEJMoa0803154.View ArticlePubMedGoogle Scholar
- Kilby JM, Hopkins S, Venetta TM, DiMassimo B, Cloud GA, Lee JY, Alldredge L, Hunter E, Lambert D, Bolognesi D, Matthews T, Johnson MR, Nowak MA, Shaw GM, Saag MS: Potent suppression of HIV-1 replication in humans by T-20, a peptide inhibitor of gp41-mediated virus entry. Nat Med. 1998, 4: 1302-1307. 10.1038/3293.View ArticlePubMedGoogle Scholar
- Lalezari JP, Henry K, O’Hearn M, Montaner JS, Piliero PJ, Trottier B, Walmsley S, Cohen C, Kuritzkes DR, Eron JJ, Matthews T, Johnson MR, Nowak MA, Shaw GM, Saag MS: Enfuvirtide, an HIV-1 fusion inhibitor, for drug-resistant HIV infection in North and South America. N Engl J Med. 2003, 348: 2175-2185. 10.1056/NEJMoa035026.View ArticlePubMedGoogle Scholar
- Wild CT, Shugars DC, Greenwell TK, McDanal CB, Matthews TJ: Peptides corresponding to a predictive alpha-helical domain of human immunodeficiency virus type 1 gp41 are potent inhibitors of virus infection. Proc Natl Acad Sci U S A. 1994, 91: 9770-9774. 10.1073/pnas.91.21.9770.PubMed CentralView ArticlePubMedGoogle Scholar
- Rimsky LT, Shugars DC, Matthews TJ: Determinants of human immunodeficiency virus type 1 resistance to gp41-derived inhibitory peptides. J Virol. 1998, 72: 986-993.PubMed CentralPubMedGoogle Scholar
- Baldwin CE, Sanders RW, Deng Y, Jurriaans S, Lange JM, Lu M, Berkhout B: Emergence of a drug-dependent human immunodeficiency virus type 1 variant during therapy with the T20 fusion inhibitor. J Virol. 2004, 78: 12428-12437. 10.1128/JVI.78.22.12428-12437.2004.PubMed CentralView ArticlePubMedGoogle Scholar
- Greenberg ML, Cammack N: Resistance to enfuvirtide, the first HIV fusion inhibitor. J Antimicrob Chemother. 2004, 54: 333-340. 10.1093/jac/dkh330.View ArticlePubMedGoogle Scholar
- Berkhout B, Eggink D, Sanders RW: Is there a future for antiviral fusion inhibitors?. Curr Opin Virol. 2012, 2: 50-59. 10.1016/j.coviro.2012.01.002.View ArticlePubMedGoogle Scholar
- Chan DC, Fass D, Berger JM, Kim PS: Core structure of gp41 from the HIV envelope glycoprotein. Cell. 1997, 89: 263-273. 10.1016/S0092-8674(00)80205-6.View ArticlePubMedGoogle Scholar
- Tan K, Liu J, Wang J, Shen S, Lu M: Atomic structure of a thermostable subdomain of HIV-1 gp41. Proc Natl Acad Sci U S A. 1997, 94: 12303-12308. 10.1073/pnas.94.23.12303.PubMed CentralView ArticlePubMedGoogle Scholar
- Weissenhorn W, Dessen A, Harrison SC, Skehel JJ, Wiley DC: Atomic structure of the ectodomain from HIV-1 gp41. Nature. 1997, 387: 426-430. 10.1038/387426a0.View ArticlePubMedGoogle Scholar
- Chan DC, Chutkowski CT, Kim PS: Evidence that a prominent cavity in the coiled coil of HIV type 1 gp41 is an attractive drug target. Proc Natl Acad Sci U S A. 1998, 95: 15613-15617. 10.1073/pnas.95.26.15613.PubMed CentralView ArticlePubMedGoogle Scholar
- Chan DC, Kim PS: HIV entry and its inhibition. Cell. 1998, 93: 681-684. 10.1016/S0092-8674(00)81430-0.View ArticlePubMedGoogle Scholar
- Eggink D, Berkhout B, Sanders RW: Inhibition of HIV-1 by fusion inhibitors. Curr Pharm Des. 2010, 16: 3716-3728. 10.2174/138161210794079218.View ArticlePubMedGoogle Scholar
- Steffen I, Pohlmann S: Peptide-based inhibitors of the HIV envelope protein and other class I viral fusion proteins. Curr Pharm Des. 2010, 16: 1143-1158. 10.2174/138161210790963751.View ArticlePubMedGoogle Scholar
- He Y: Synthesized peptide inhibitors of HIV-1 gp41-dependent membrane fusion. Curr Pharm Des. 2013, 19: 1800-1809. 10.2174/1381612811319100004.View ArticlePubMedGoogle Scholar
- Naito T, Izumi K, Kodama E, Sakagami Y, Kajiwara K, Nishikawa H, Watanabe K, Sarafianos SG, Oishi S, Fujii N, Matsuoka M: SC29EK, a peptide fusion inhibitor with enhanced alpha-helicity, inhibits replication of human immunodeficiency virus type 1 mutants resistant to enfuvirtide. Antimicrob Agents Chemother. 2009, 53: 1013-1018. 10.1128/AAC.01211-08.PubMed CentralView ArticlePubMedGoogle Scholar
- Dwyer JJ, Wilson KL, Davison DK, Freel SA, Seedorff JE, Wring SA, Tvermoes NA, Matthews TJ, Greenberg ML, Delmedico MK: Design of helical, oligomeric HIV-1 fusion inhibitor peptides with potent activity against enfuvirtide-resistant virus. Proc Natl Acad Sci U S A. 2007, 104: 12772-12777. 10.1073/pnas.0701478104.PubMed CentralView ArticlePubMedGoogle Scholar
- He Y, Xiao Y, Song H, Liang Q, Ju D, Chen X, Lu H, Jing W, Jiang S, Zhang L: Design and evaluation of sifuvirtide, a novel HIV-1 fusion inhibitor. J Biol Chem. 2008, 283: 11126-11134. 10.1074/jbc.M800200200.View ArticlePubMedGoogle Scholar
- Chong H, Yao X, Qiu Z, Qin B, Han R, Waltersperger S, Wang M, Cui S, He Y: Discovery of critical residues for viral entry and inhibition through structural Insight of HIV-1 fusion inhibitor CP621-652. J Biol Chem. 2012, 287: 20281-20289. 10.1074/jbc.M112.354126.PubMed CentralView ArticlePubMedGoogle Scholar
- Chong H, Yao X, Sun J, Qiu Z, Zhang M, Waltersperger S, Wang M, Cui S, He Y: The M-T hook structure is critical for design of HIV-1 fusion inhibitors. J Biol Chem. 2012, 287: 34558-34568. 10.1074/jbc.M112.390393.PubMed CentralView ArticlePubMedGoogle Scholar
- Chong H, Yao X, Qiu Z, Sun J, Zhang M, Waltersperger S, Wang M, Liu SL, Cui S, He Y: Short-peptide fusion inhibitors with high potency against wild-type and enfuvirtide-resistant HIV-1. FASEB J. 2013, 27: 1203-1213. 10.1096/fj.12-222547.View ArticlePubMedGoogle Scholar
- He Y, Liu S, Li J, Lu H, Qi Z, Liu Z, Debnath AK, Jiang S: Conserved salt bridge between the N- and C-terminal heptad repeat regions of the human immunodeficiency virus type 1 gp41 core structure is critical for virus entry and inhibition. J Virol. 2008, 82: 11129-11139. 10.1128/JVI.01060-08.PubMed CentralView ArticlePubMedGoogle Scholar
- Nameki D, Kodama E, Ikeuchi M, Mabuchi N, Otaka A, Tamamura H, Ohno M, Fujii N, Matsuoka M: Mutations conferring resistance to human immunodeficiency virus type 1 fusion inhibitors are restricted by gp41 and Rev-responsive element functions. J Virol. 2005, 79: 764-770. 10.1128/JVI.79.2.764-770.2005.PubMed CentralView ArticlePubMedGoogle Scholar
- He Y, Cheng J, Li J, Qi Z, Lu H, Dong M, Jiang S, Dai Q: Identification of a critical motif for the human immunodeficiency virus type 1 (HIV-1) gp41 core structure: implications for designing novel anti-HIV fusion inhibitors. J Virol. 2008, 82: 6349-6358. 10.1128/JVI.00319-08.PubMed CentralView ArticlePubMedGoogle Scholar
- He Y, Cheng J, Lu H, Li J, Hu J, Qi Z, Liu Z, Jiang S, Dai Q: Potent HIV fusion inhibitors against Enfuvirtide-resistant HIV-1 strains. Proc Natl Acad Sci U S A. 2008, 105: 16332-16337. 10.1073/pnas.0807335105.PubMed CentralView ArticlePubMedGoogle Scholar
- Naider F, Anglister J: Peptides in the treatment of AIDS. Curr Opin Struct Biol. 2009, 19: 473-482. 10.1016/j.sbi.2009.07.003.PubMed CentralView ArticlePubMedGoogle Scholar
- Mink M, Mosier SM, Janumpalli S, Davison D, Jin L, Melby T, Sista P, Erickson J, Lambert D, Stanfield-Oakley SA, Salgo M, Cammack N, Matthews T, Greenberg ML: Impact of human immunodeficiency virus type 1 gp41 amino acid substitutions selected during enfuvirtide treatment on gp41 binding and antiviral potency of enfuvirtide in vitro. J Virol. 2005, 79: 12447-12454. 10.1128/JVI.79.19.12447-12454.2005.PubMed CentralView ArticlePubMedGoogle Scholar
- Sista PR, Melby T, Davison D, Jin L, Mosier S, Mink M, Nelson EL, DeMasi R, Cammack N, Salgo MP, Matthews T, Greenberg ML: Characterization of determinants of genotypic and phenotypic resistance to enfuvirtide in baseline and on-treatment HIV-1 isolates. AIDS. 2004, 18: 1787-1794. 10.1097/00002030-200409030-00007.View ArticlePubMedGoogle Scholar
- Liu Z, Shan M, Li L, Lu L, Meng S, Chen C, He Y, Jiang S, Zhang L: In vitro selection and characterization of HIV-1 variants with increased resistance to sifuvirtide, a novel HIV-1 fusion inhibitor. J Biol Chem. 2011, 286: 3277-3287. 10.1074/jbc.M110.199323.PubMed CentralView ArticlePubMedGoogle Scholar
- Shimura K, Nameki D, Kajiwara K, Watanabe K, Sakagami Y, Oishi S, Fujii N, Matsuoka M, Sarafianos SG, Kodama EN: Resistance profiles of novel electrostatically constrained HIV-1 fusion inhibitors. J Biol Chem. 2010, 285: 39471-39480. 10.1074/jbc.M110.145789.PubMed CentralView ArticlePubMedGoogle Scholar
- Eggink D, Bontjer I, Langedijk JP, Berkhout B, Sanders RW: Resistance of human immunodeficiency virus type 1 to a third-generation fusion inhibitor requires multiple mutations in gp41 and is accompanied by a dramatic loss of gp41 function. J Virol. 2011, 85: 10785-10797. 10.1128/JVI.05331-11.PubMed CentralView ArticlePubMedGoogle Scholar
- Eggink D, Langedijk JP, Bonvin AM, Deng Y, Lu M, Berkhout B, Sanders RW: Detailed mechanistic insights into HIV-1 sensitivity to three generations of fusion inhibitors. J Biol Chem. 2009, 284: 26941-26950. 10.1074/jbc.M109.004416.PubMed CentralView ArticlePubMedGoogle Scholar
- Yao X, Chong H, Zhang C, Waltersperger S, Wang M, Cui S, He Y: Broad antiviral activity and crystal structure of HIV-1 fusion inhibitor sifuvirtide. J Biol Chem. 2012, 287: 6788-6796. 10.1074/jbc.M111.317883.PubMed CentralView ArticlePubMedGoogle Scholar
- Julien JP, Cupo A, Sok D, Stanfield RL, Lyumkis D, Deller MC, Klasse PJ, Burton DR, Sanders RW, Moore JP, Ward AB, Wilson IA: Crystal structure of a soluble cleaved HIV-1 envelope trimer. Science. 2013, 342: 1477-1483. 10.1126/science.1245625.View ArticlePubMedGoogle Scholar
- Lyumkis D, Julien JP, de Val N, Cupo A, Potter CS, Klasse PJ, Burton DR, Sanders RW, Moore JP, Carragher B, Wilson IA, Ward AB: Cryo-EM structure of a fully glycosylated soluble cleaved HIV-1 envelope trimer. Science. 2013, 342: 1484-1490. 10.1126/science.1245627.PubMed CentralView ArticlePubMedGoogle Scholar
- Bartesaghi A, Merk A, Borgnia MJ, Milne JL, Subramaniam S: Prefusion structure of trimeric HIV-1 envelope glycoprotein determined by cryo-electron microscopy. Nat Struct Mol Biol. 2013, 20: 1352-1357. 10.1038/nsmb.2711.PubMed CentralView ArticlePubMedGoogle Scholar
- Gill SC, von Hippel PH: Calculation of protein extinction coefficients from amino acid sequence data. Anal Biochem. 1989, 182: 319-326. 10.1016/0003-2697(89)90602-7.View ArticlePubMedGoogle Scholar
- Chong H, Yao X, Zhang C, Cai L, Cui S, Wang Y, He Y: Biophysical property and broad anti-HIV activity of albuvirtide, a 3-maleimimidopropionic acid-modified peptide fusion inhibitor. PLoS One. 2012, 7: e32599-10.1371/journal.pone.0032599.PubMed CentralView ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.