An architecture for the fusion site of Influenza hemagglutinin

Bentz, Joe; Ellens, Harma; Alford, Dennis R.

doi:10.1016/0014-5793(90)80492-2

Cited by 95 publications

(85 citation statements)

References 27 publications

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“…Proteinaceous Versus Lipidic Fusion Pores-Our data would be quite compatible with the numerous models proposing that fusion is the result of complex formation by multiple HA molecules in a ring-like structure (35,40,(42)(43)(44), assuming that the small pores correspond to the action of individual HA trimers before complex formation (Fig. 7a) and that the large pores are caused by the complex.…”

Section: Discussionsupporting

confidence: 75%

“…Thus, most likely, pores increase in size gradually by recruiting additional trimers. Such behavior has been described for HA-induced fusion pore formation, and large pores are thought to be formed following complex formation by multiple HA trimers (17,18,40,41), again suggesting that fusion and leakage pores are related structures. A new element contributed by our observations is that since large leakage pores would be formed in a similar way, the target membrane half of the fusion pore may initially be a leakage pore (Fig.…”

Section: Discussionmentioning

confidence: 99%

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Membrane Perturbation and Fusion Pore Formation in Influenza Hemagglutinin-mediated Membrane Fusion

Bonnafous

Stegmann

2000

Journal of Biological Chemistry

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Low pH-induced fusion mediated by the hemagglutinin (HA) of influenza virus involves conformational changes in the protein that lead to the insertion of a "fusion peptide" domain of this protein into the target membrane and is thought to perturb the membrane, triggering fusion. By using whole virus, purified HA, or HA ectodomains, we found that shortly after insertion, pores of less than 26 Å in diameter were formed in liposomal membranes. As measured by a novel assay, these pores stay open, or continue to close and open, for minutes to hours and persist after pH neutralization. With virus and purified HA, larger pores, allowing the leakage of dextrans, were seen at times well after insertion. For virus, dextran leakage was simultaneous with lipid mixing and the formation of "fusion pores," allowing the transfer of dextrans from the liposomal to the viral interior or vice versa. Pores did not form in the viral membrane in the absence of a target membrane. Based on these data, we propose a new model for fusion, in which HA initially forms a proteinaceous pore in the target, but not in the viral membrane, before a lipidic hemifusion intermediate is formed.

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Section: Discussionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Membrane Perturbation and Fusion Pore Formation in Influenza Hemagglutinin-mediated Membrane Fusion

Bonnafous

Stegmann

2000

Journal of Biological Chemistry

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“…For viral fusion proteins, fusion could be driven by destabilization of the membranes by the fusion peptide, by energy released by the spring-loaded conformational change or other conformational changes, or by some combination of the two. Models for HAmediated fusion that do not require the spring-loaded conformational change but rather rely primarily on the fusion peptide have been proposed (3,5,26). Our findings, however, argue strongly that binding of the fusion peptides to the target membrane is not sufficient.…”

Section: Discussionmentioning

confidence: 52%

“…Because it seems apparent that some head group separation is required for complete coiled-coil formation, it was argued that fusion occurs prior to the springloaded conformational change. These and other lines of evidence led to alternate models for HA fusion which do not require the spring-loaded conformational change (3,5,26) (see Discussion).…”

mentioning

confidence: 92%

New Insights into the Spring-Loaded Conformational Change of Influenza Virus Hemagglutinin

Gruenke¹,

Armstrong²,

Newcomb

et al. 2002

J Virol

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Influenza virus hemagglutinin undergoes a conformational change in which a loop-to-helix "spring-loaded" conformational change forms a coiled coil that positions the fusion peptide for interaction with the target bilayer. Previous work has shown that two proline mutations designed to disrupt this change disrupt fusion but did not determine the basis for the fusion defect. In this work, we made six additional mutants with single proline substitutions in the region that undergoes the spring-loaded conformational change and two additional mutants with double proline substitutions in this region. All double mutants were fusion inactive. We analyzed one double mutant, F63P/F70P, as an example. We observed that F63P/F70P undergoes key low-pH-induced conformational changes and binds tightly to target membranes. However, limited proteolysis and electron microscopy observations showed that the mutant forms a coiled coil that is only ϳ50% the length of the wild type, suggesting that it is splayed in its N-terminal half. This work further supports the hypothesis that the spring-loaded conformational change is necessary for fusion. Our data also indicate that the spring-loaded conformational change has another role beyond presenting the fusion peptide to the target membrane.

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“…Even so, it is still possible that the presence of the scFv domain may be interfering with the fusion process in some way, perhaps by obstructing the access of the fusion peptide to the target membrane, or by blocking a downstream step in the fusion process, such as the aggregation of trimers which has been postulated to be necessary for fusion to proceed. 34 A second possible reason for the lack of fusion activity may be that the CHO407c cells do not produce enough of the chimaeric protein to initiate fusion. It has been shown previously 20 that a higher surface density of HA is needed to initiate fusion than to cause haemadsorption; perhaps the level of chimaeric protein produced by the CHO407c cells falls in between these two thresholds.…”

Section: After Rolling At Room Temperature For 1 H Unbound Nip-cap-omentioning

confidence: 99%

Antigen-specific membrane fusion mediated by the haemagglutinin protein of influenza A virus: separation of attachment and fusion functions on different molecules

1999

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Using genetic engineering techniques, two strategies for brane fusion functions of HA on to two different molecules. changing the receptor-binding specificity of the influenzaThe feasibility of this strategy was tested by looking for A virus haemagglutinin (HA) protein whilst preserving its fusion between NIP-conjugated red blood cells which membrane fusion function, have been explored. approach using a different virus attachment/entry protein with well understood structure-to-function relationships. The haemagglutinin (HA) protein of influenza A virus fits this description since it has been exceptionally well characterised in terms of both three-dimensional structure and function. [17][18][19] The HA protein's role in influenza virus replication is to bind the virus to potential host cells by interacting with sialic acid residues on the cell surface, and then to mediate virus entry into the cell by fusing together the virus envelope and cell membrane in a low pH-dependent process. 20 It is initially synthesised as a single monomeric polypeptide, HA0, which is subsequently cleaved by a nonviral protease into two polypeptides, HA1 and HA2, linked together by a disulphide bond. This cleavage process is essential for its fusion activity. In terms of three-dimensional structure, HA consists of a membrane-distal globular head joined by a hinge to a stem region, the end of which is embedded in the virus envelope (or infected cell membrane). The globular head, formed from the HA1 polypeptide, carries the sialic acid receptor binding site. The stem, formed from HA2 and components of HA1, contains the region responsible for mediating fusion. After synthesis,

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An architecture for the fusion site of Influenza hemagglutinin

Cited by 95 publications

References 27 publications

Membrane Perturbation and Fusion Pore Formation in Influenza Hemagglutinin-mediated Membrane Fusion

Membrane Perturbation and Fusion Pore Formation in Influenza Hemagglutinin-mediated Membrane Fusion

New Insights into the Spring-Loaded Conformational Change of Influenza Virus Hemagglutinin

Antigen-specific membrane fusion mediated by the haemagglutinin protein of influenza A virus: separation of attachment and fusion functions on different molecules

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