Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex

<p>Abstract</p> <p>Background</p> <p>To study the organization and interaction with the fusion domain (or fusion peptide, FP) of the transmembrane domain (TMD) of influenza virus envelope glycoprotein for its role in membrane fusion which is also essential in the cellular trafficking of biomolecules and sperm-egg fusion.</p> <p>Results</p> <p>The fluorescence and gel electrophoresis experiments revealed a tight self-assembly of TMD in the model membrane. A weak but non-random interaction between TMD and FP in the membrane was found. In the complex, the central TMD oligomer was packed by FP in an antiparallel fashion. FP insertion into the membrane was altered by binding to TMD. An infrared study exhibited an enhanced membrane perturbation by the complex formation. A model was built to illustrate the role of TMD in the late stages of influenza virus-mediated membrane fusion reaction.</p> <p>Conclusion</p> <p>The TMD oligomer anchors the fusion protein in the membrane with minimal destabilization to the membrane. Upon associating with FP, the complex exerts a synergistic effect on the membrane perturbation. This effect is likely to contribute to the complete membrane fusion during the late phase of fusion protein-induced fusion cascade. The results presented in the work characterize the nature of the interaction of TMD with the membrane and TMD in a complex with FP in the steps leading to pore initiation and dilation during virus-induced fusion. Our data and proposed fusion model highlight the key role of TMD-FP interaction and have implications on the fusion reaction mediated by other type I viral fusion proteins. Understanding the molecular mechanism of membrane fusion may assist in the design of anti-viral drugs.</p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex

<p>Abstract</p> <p>Background</p> <p>To study the organization and interaction with the fusion domain (or fusion peptide, FP) of the transmembrane domain (TMD) of influenza virus envelope glycoprotein for its role in membrane fusion which is also essential in the cellular trafficking of biomolecules and sperm-egg fusion.</p> <p>Results</p> <p>The fluorescence and gel electrophoresis experiments revealed a tight self-assembly of TMD in the model membrane. A weak but non-random interaction between TMD and FP in the membrane was found. In the complex, the central TMD oligomer was packed by FP in an antiparallel fashion. FP insertion into the membrane was altered by binding to TMD. An infrared study exhibited an enhanced membrane perturbation by the complex formation. A model was built to illustrate the role of TMD in the late stages of influenza virus-mediated membrane fusion reaction.</p> <p>Conclusion</p> <p>The TMD oligomer anchors the fusion protein in the membrane with minimal destabilization to the membrane. Upon associating with FP, the complex exerts a synergistic effect on the membrane perturbation. This effect is likely to contribute to the complete membrane fusion during the late phase of fusion protein-induced fusion cascade. The results presented in the work characterize the nature of the interaction of TMD with the membrane and TMD in a complex with FP in the steps leading to pore initiation and dilation during virus-induced fusion. Our data and proposed fusion model highlight the key role of TMD-FP interaction and have implications on the fusion reaction mediated by other type I viral fusion proteins. Understanding the molecular mechanism of membrane fusion may assist in the design of anti-viral drugs.</p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex-6

Nd is assigned to hydrated hydrogen bonded lipid. It is seen that the percentage of dehydrated bands increases as the two peptides form a complex and FP has a higher dehydration level than TMD.<p><b>Copyright information:</b></p><p>Taken from "Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex"</p><p>http://www.biomedcentral.com/1741-7007/6/2</p><p>BMC Biology 2008;6():2-2.</p><p>Published online 15 Jan 2008</p><p>PMCID:PMC2267159.</p><p></p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex-0

Let of the bilayer is minimally disrupted by FP with an oblique insertion angle. Note the loose FP self-assembly and tight self-association of TMD in the membrane. (2) Low pH-induced refolding of HR1 and HR2 regions of the HA2 driven by strong interactions between them. The two apposing membranes are pulled in proximity and bulged-out to facilitate the merge. (3) Driven by the energy liberated by HR1-HR2 association and additional force provided by the polar, conformationally plastic linker segment downstream of FP and the membranetropic pre-TM region, the two fusing membranes undergo dehydration, deformation and coalescence of the outer leaflets, causing hemifusion. In the process, the compact TMD homo-trimer approaches the loose FP aggregate and may be interspersed with FP molecules, gradually forming the TMD-FP complex, which is not specific per se, with TMD in the inner core. Nonetheless, the interaction is sufficiently strong to align FP with TMD to a certain extent and deepen FP penetration into the inner leaflet, further destabilizing the bilayer. (4) Partly as a result of the complex formation-enhanced perturbation of both leaflets of the effector and target membranes, the hemifusion diaphragm transits to an inceptive fusion pore, concomitant with the six-helix bundle formation of HR1 and HR2. By this stage, the recruitment of adjacent TMD:FP triplex subunits cooperatively stabilizes the initial pore and its dilation to facilitate the mixing of cytoplasmic contents.<p><b>Copyright information:</b></p><p>Taken from "Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex"</p><p>http://www.biomedcentral.com/1741-7007/6/2</p><p>BMC Biology 2008;6():2-2.</p><p>Published online 15 Jan 2008</p><p>PMCID:PMC2267159.</p><p></p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex-2

N between the two molecules. Different combinations are depicted by various curves as indicated and the dashed curve is derived from random distribution of = 60 Å donor-acceptor pair [36]. Higher FRET efficiency from experimental data for the labeled NBD-Rho pair than that from the theoretical computation at any given Rhodamine concentration suggests association between TMD and FP in the membrane bilayer.<p><b>Copyright information:</b></p><p>Taken from "Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex"</p><p>http://www.biomedcentral.com/1741-7007/6/2</p><p>BMC Biology 2008;6():2-2.</p><p>Published online 15 Jan 2008</p><p>PMCID:PMC2267159.</p><p></p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex-1

Beled TMD manifests packing of TMD molecules into a tight subunit in the membrane at pH 5.0 and 7.4. In contrast, labeled FP exhibits less self-quenching, indicative of a loose association for the peptide molecules. (B) Association between TMD and FP in the bilayer is not arbitrary as FP of HIV-1 gp41 causes no change in Rho-TMD dequenching or Rho-FP of gp41 dequenching was not affected by mixing with TMD. Change in Rho-FP or Rho-TMD of HA2, in contrast, is obvious when complexed to their counterpart. Note that the smallest value of in the measurements is 0.02 for (A) and 0.05 for (B). (C) A higher propensity of self-association for TMD than FP is revealed by SDS-PAGE. Lanes 1 and 2 show that FP has less tendency than TMD to form oligomers in SDS in either neutral or acidic buffer. In contrast, TMD formed multiple oligomeric species (lane 4) at pH 4.8 for which minimal association owing to disulfide linkage is expected. The association between TMD and FP is not strong enough to sustain the dispersing force of SDS detergent and the electric field as seen in lane 3.<p><b>Copyright information:</b></p><p>Taken from "Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex"</p><p>http://www.biomedcentral.com/1741-7007/6/2</p><p>BMC Biology 2008;6():2-2.</p><p>Published online 15 Jan 2008</p><p>PMCID:PMC2267159.</p><p></p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex-7

Sicles attest to the location of TMD in the membrane hydrophobic milieu. The emission maximum for tryptophan in an aqueous environment is 350 nm. (B) acrylamide quenching measurements also indicate deep insertion of TMD into the membrane interior. The dramatic decrease in in the vesicular dispersion compared with that in PB buffer shows that tryptophan side chains are embedded deep into the membrane. Moreover, a twofold reduction in , as well as decreased on neutralization, upon incubating in PC:PG vesicles at pH 5.0 compared with that at pH 7.4 suggests that the TMD penetration is deeper at acidic pH.<p><b>Copyright information:</b></p><p>Taken from "Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex"</p><p>http://www.biomedcentral.com/1741-7007/6/2</p><p>BMC Biology 2008;6():2-2.</p><p>Published online 15 Jan 2008</p><p>PMCID:PMC2267159.</p><p></p

Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex-4

Nteracting with TMD can be rationalized by a better alignment of FP on complexing to TMD. The results also support the notion of FP-TMD interaction in the membrane.<p><b>Copyright information:</b></p><p>Taken from "Membrane interaction and structure of the transmembrane domain of influenza hemagglutinin and its fusion peptide complex"</p><p>http://www.biomedcentral.com/1741-7007/6/2</p><p>BMC Biology 2008;6():2-2.</p><p>Published online 15 Jan 2008</p><p>PMCID:PMC2267159.</p><p></p