To understand how viral proteins fuse with the cell membrane, a process that is important for the initial stages of infection, the conformation of the membrane-bound viral fusion peptides (FPs) must be identified. Here, molecular dynamics (MD) simulations were performed to investigate the conformation of the FP-16 and FP-23 of human immunodeficiency virus (HIV) bound to a dimyristoyl phosphatidylcholine (DMPC) bilayer. All FPs were found to penetrate into the bilayer despite the different initial orientations. In addition, the inclusion of residues 17 to 23 was found to play significant role in the fusion ability. Each of the FPs adopts at least two distinct conformations (predominantly α-helical and β-structures) while association with membrane. The peptide seriously affects structural and dynamical parameter of the contacted lipids. The previously experimental data together with our simulation data reveal that fusion ability depends on the membrane-associated conformation and alignment of the peptide.

2011-04-01·European Biophysics Journal4区 · 生物学

Irregular structure of the HIV fusion peptide in membranes demonstrated by solid-state NMR and MD simulations

4区 · 生物学

Article

作者: Dorit Grasnick ; Erik Strandberg ; Parvesh Wadhwani ; Anne S. Ulrich ; Ulrich Sternberg

To better understand peptide-induced membrane fusion at a molecular level, we set out to determine the structure of the fusogenic peptide FP23 from the HIV-1 protein gp41 when bound to a lipid bilayer. An established solid-state (19)F nuclear magnetic resonance (NMR) approach was used to collect local orientational constraints from a series of CF(3)-phenylglycine-labeled peptide analogues in macroscopically aligned membranes. Fusion assays showed that these (19)F-labels did not significantly affect peptide function. The NMR spectra were characteristic of well-behaved samples, without any signs of heterogeneity or peptide aggregation at 1:300 in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC). We can conclude from these NMR data that FP23 has a well-defined (time-averaged) conformation and undergoes lateral diffusion in the bilayer plane, presumably as a monomer or small oligomer. Attempts to evaluate its conformation in terms of various secondary structures, however, showed that FP23 does not form any type of regular helix or β-strand. Therefore, all-atom molecular dynamics (MD) simulations were carried out using the orientational NMR constraints as pseudo-forces to drive the peptide into a stable alignment and structure. The resulting picture suggests that FP23 can adopt multiple β-turns and insert obliquely into the membrane. Such irregular conformation explains why the structure of the fusion peptide could not be reliably determined by any biophysical method so far.

2010-11-01·Microbes and Infection3区 · 医学

The encapsulated strain TIGR4 of Streptococcus pneumoniae is phagocytosed but is resistant to intracellular killing by mouse microglia

3区 · 医学

Article

作者: Elena Righi ; Marco Rinaldo Oggioni ; Velia Braione ; Michele Zoli ; Susanna Ricci ; Massimino Messinò ; Sergio Tripodi ; Elisabetta Blasi ; Samuele Peppoloni ; Marcella Cintorino ; Carlotta F. Orsi ; Giuliana Fabio ; Maria Margherita De Santi ; Gianni Pozzi ; Bruna Colombari ; Alessio Zanardi ; Damiana Chiavolini

The polysaccharide capsule is a major virulence factor of Streptococcus pneumoniae as it confers resistance to phagocytosis. The encapsulated serotype 4 TIGR4 strain was shown to be efficiently phagocytosed by the mouse microglial cell line BV2, whereas the type 3 HB565 strain resisted phagocytosis. Comparing survival after uptake of TIGR4 or its unencapsulated derivative FP23 in gentamicin protection and phagolysosome maturation assays, it was shown that TIGR4 was protected from intracellular killing. Pneumococcal capsular genes were up-regulated in intracellular TIGR4 bacteria recovered from microglial cells. Actual presence of bacteria inside BV2 cells was confirmed by transmission electron microscopy (TEM) for both TIGR4 and FP23 strains, but typical phagosomes/phagolysosomes were detected only in cells infected with the unencapsulated strain. In a mouse model of meningitis based on intracranic inoculation of pneumococci, TIGR4 caused lethal meningitis with an LD(50) of 2 × 10² CFU, whereas the LD(50) for the unencapsulated FP23 was greater than 10⁷ CFU. Phagocytosis of TIGR4 by microglia was also demonstrated by TEM and immunohistochemistry on brain samples from infected mice. The results indicate that encapsulation does not protect the TIGR4 strain from phagocytosis by microglia, while it affords resistance to intracellular killing.

100 项与 FP-0023 相关的药物交易

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