enfuvirtide and 1-palmitoyl-2-oleoylphosphatidylcholine

T-20 and T-1249 fusion inhibitor peptides were shown to interact with 1-palmitoyl-2-oleyl-phosphatidylcholine (POPC) (liquid disordered, ld) and POPC/cholesterol (1:1) (POPC/Chol) (liquid ordered, lo) bilayers, and they do so to different extents. Although they both possess a tryptophan-rich domain (TRD), T-20 lacks a pocket binding domain (PBD), which is present in T-1249. It has been postulated that the PBD domain enhances FI interaction with HIV gp41 protein and with model membranes. Interaction of these fusion inhibitor peptides with both the cell membrane and the viral envelope membrane is important for function, i.e., inhibition of the fusion process. We address this problem with a molecular dynamics approach focusing on lipid properties, trying to ascertain the consequences and the differences in the interaction of T-20 and T-1249 with ld and lo model membranes. T-20 and T-1249 interactions with model membranes are shown to have measurable and different effects on bilayer structural and dynamical parameters. T-1249's adsorption to the membrane surface has generally a stronger influence in the measured parameters. The presence of both binding domains in T-1249 appears to be paramount to its stronger interaction, and is shown to have a definite importance in membrane properties upon peptide adsorption.

Topics: Cholesterol; Enfuvirtide; HIV; HIV Envelope Protein gp41; HIV Fusion Inhibitors; Humans; Hydrogen Bonding; Lipid Bilayers; Molecular Dynamics Simulation; Peptide Fragments; Peptides; Phosphatidylcholines; Protein Binding; Protein Structure, Tertiary

T-20 (also known as enfuvirtide) is a fusion inhibitor peptide known to have some effectiveness in the control of progression of HIV infection by inhibiting the fusion of the HIV envelope with the target cell membrane. Recent results indicate that T-20 is able to interact with membranes in the liquid disordered state but not with membranes in an ordered state, which could be linked to its effectiveness. A detailed molecular picture of the interaction of these molecules with membranes is still lacking. To this effect, extensive molecular dynamics simulations (100 ns) were carried out to investigate the interaction between T-20 and bilayers of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and POPC/cholesterol (1:1). Membrane properties such as area/lipid, density profiles, order parameters and membrane thickness were studied. It was observed that T-20 has the ability to interact to different extents with both model membranes in this study and that peptide interaction with the bilayer surface has a local effect on membrane structure. The formation of hydrogen bonding between certain peptide residues and the POPC phosphate group was observed. However, T-20 showed a more limited extent of interaction with model membranes when compared with other, more efficient, peptides (such as T-1249). This effect is most notable in POPC/Chol membranes in which interaction is especially weak, owing to less peptide residues acting as H bond donors to POPC and virtually no H bonds being formed between T-20 and cholesterol. This lower ability to interact with membranes is probably correlated with its smaller inhibitory efficiency.

Topics: Cholesterol; Enfuvirtide; HIV; HIV Envelope Protein gp41; HIV Fusion Inhibitors; HIV Infections; Humans; Lipid Bilayers; Molecular Dynamics Simulation; Peptide Fragments; Phosphatidylcholines

Sifuvirtide, a 36 amino acid negatively charged peptide, is a novel and promising HIV fusion inhibitor, presently in clinical trials. Because of the aromatic amino acid residues of the peptide, its behavior in aqueous solution and the interaction with lipid-membrane model systems (large unilammelar vesicles) were studied by using mainly fluorescence spectroscopy techniques (both steady-state and time-resolved). No significant aggregation of the peptide was observed with aqueous solution. Various biological and nonbiological lipid-membrane compositions were analyzed, and atomic force microscopy was used to visualize phase separation in several of those mixtures. Results showed no significant interaction of the peptide, neither with zwitterionic fluid lipid membranes (liquid-disordered phase), nor with cholesterol-rich membranes (liquid-ordered phase). However, significant partitioning was observed with the positively charged lipid models (K(p) = (2.2 +/- 0.3) x 10(3)), serving as a positive control. Fluorescence quenching using Förster resonance acrylamide and lipophilic probes was carried out to study the location of the peptide in the membrane models. In the gel-phase DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) membrane model, an adsorption of the peptide at the surface of these membranes was observed and confirmed by using Förster resonance energy-transfer experiments. These results indicate a targeting of the peptide to gel-phase domains relatively to liquid-disordered or liquid-ordered phase domains. This larger affinity and selectivity toward the more rigid areas of the membranes, where most of the receptors are found, or to viral membrane, may help explain the improved clinical efficiency of sifuvirtide, by providing a local increased concentration of the peptide at the fusion site.

Topics: Acrylamide; Amino Acid Sequence; Enfuvirtide; Fluorescence Resonance Energy Transfer; HIV Envelope Protein gp41; HIV Fusion Inhibitors; Lipid Bilayers; Membrane Fluidity; Membrane Lipids; Molecular Sequence Data; Peptide Fragments; Peptides; Phosphatidylcholines; Phosphatidylglycerols; Solutions; Water

The envelope spike (S) glycoprotein of the severe acute respiratory syndrome associated coronavirus (SARS-CoV) mediates the entry of the virus into target cells. Recent studies point out to a cell entry mechanism of this virus similar to other enveloped viruses, such as HIV-1. As it happens with other viruses peptidic fusion inhibitors, SARS-CoV S protein HR2-derived peptides are potential therapeutic drugs against the virus. It is believed that HR2 peptides block the six-helix bundle formation, a key structure in the viral fusion, by interacting with the HR1 region. It is a matter of discussion if the HIV-1 gp41 HR2-derived peptide T20 (enfuvirtide) could be a possible SARS-CoV inhibitor given the similarities between the two viruses. We tested the possibility of interaction between both T20 (HIV-1 gp41 HR2-derived peptide) and T-1249 with S protein HR1- and HR2-derived peptides. Our biophysical data show a significant interaction between a SARS-CoV HR1-derived peptide and T20. However, the interaction is only moderate (K(B)=(1.1+/-0.3)x10(5) M(-1)). This finding shows that the reasoning behind the hypothesis that T20, already approved for clinical application in AIDS treatment, could inhibit the fusion of SARS-CoV with target cells is correct but the effect may not be strong enough for application.

Topics: Amino Acid Sequence; Enfuvirtide; HIV Envelope Protein gp41; HIV Fusion Inhibitors; Hydrophobic and Hydrophilic Interactions; Liposomes; Peptide Fragments; Phosphatidylcholines; Severe acute respiratory syndrome-related coronavirus; Viral Fusion Proteins

T-1249 is a HIV fusion inhibitor peptide under clinical trials. Its interaction with biological membrane models (large unilamellar vesicles) was studied using fluorescence spectroscopy. A gp41 peptide that includes one of the hydrophobic terminals of T-1249 was also studied. Both peptides partition extensively to liquid-crystalline POPC (1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine) (DeltaG = -7.0 kcal/mol and -8.7 kcal/mol, for T-1249 and terminal peptide, respectively) and are located at the interface of the membrane. T-1249 is essentially in a random coil conformation in this lipidic medium, although a small alpha-helix contribution is present. When other lipid compositions are used (DPPC, POPG + POPC, and POPC + cholesterol) (DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) and POPG (1-palmitoyl-2-oleyl-sn-glycero-3-[phospho-rac-(1-glycerol)), partition decreases, the most severe effect being the presence of cholesterol. Partition experiments and fluorescence resonance energy transfer analysis show that T-1249 adsorbs to cholesterol-rich membranes. The improved clinical efficiency of T-1249 relative to enfuvirtide (T20) may be related to its bigger partition coefficient and ability to adsorb to rigid lipidic areas on the cell surface, where most receptors are inserted. Moreover, adsorption to the sterol-rich viral membrane helps to increase the local concentration of the inhibitor peptide at the fusion site.

Topics: Amino Acid Sequence; Cholesterol; Enfuvirtide; Fluorescence Resonance Energy Transfer; HIV Envelope Protein gp41; Kinetics; Lipid Bilayers; Membranes, Artificial; Models, Molecular; Molecular Sequence Data; Peptide Fragments; Phosphatidylcholines; Sequence Homology, Amino Acid; Spectrometry, Fluorescence; Thermodynamics