Capture and imaging of a prehairpin fusion intermediate of the paramyxovirus PIV5

Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 12/2011; 108(52):20992-7. DOI: 10.1073/pnas.1116034108
Source: PubMed


During cell entry, enveloped viruses fuse their viral membrane with a cellular membrane in a process driven by energetically favorable, large-scale conformational rearrangements of their fusion proteins. Structures of the pre- and postfusion states of the fusion proteins including paramyxovirus PIV5 F and influenza virus hemagglutinin suggest that this occurs via two intermediates. Following formation of an initial complex, the proteins structurally elongate, driving a hydrophobic N-terminal "fusion peptide" away from the protein surface into the target membrane. Paradoxically, this first conformation change moves the viral and cellular bilayers further apart. Next, the fusion proteins form a hairpin that drives the two membranes into close opposition. While the pre- and postfusion hairpin forms have been characterized crystallographically, the transiently extended prehairpin intermediate has not been visualized. To provide evidence for this extended intermediate we measured the interbilayer spacing of a paramyxovirus trapped in the process of fusing with solid-supported bilayers. A gold-labeled peptide that binds the prehairpin intermediate was used to stabilize and specifically image F-proteins in the prehairpin intermediate. The interbilayer spacing is precisely that predicted from a computational model of the prehairpin, providing strong evidence for its structure and functional role. Moreover, the F-proteins in the prehairpin conformation preferentially localize to a patch between the target and viral membranes, consistent with the fact that the formation of the prehairpin is triggered by local contacts between F- and neighboring viral receptor-binding proteins (HN) only when HN binds lipids in its target membrane.

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    • "Since E2 does not contain any clearly recognizable fusion motifs to insert into the host cell membrane, E1 is thought to bear the fusion motif in pestiviruses (El Omari et al., 2013; Li et al., 2013). If so, E1 would have to at least transiently extend to span the distance between the cellular and viral membranes prior to membrane fusion, approximately 20 nm (Kim et al., 2011). With only 177 amino acids in its ectodomain, or 143 amino acids excluding the predicted perimembrane helices, E1 would have to adopt a highly elongated fold in order to span 20 nm. "
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    ABSTRACT: The membrane anchors of viral envelope proteins play essential roles in cell entry. Recent crystal structures of the ectodomain of envelope protein E2 from a pestivirus suggest that E2 belongs to a novel structural class of membrane fusion machinery. Based on geometric constraints from the E2 structures, we generated atomic models of the E1 and E2 membrane anchors using computational approaches. The E1 anchor contains two amphipathic perimembrane helices and one transmembrane helix; the E2 anchor contains a short helical hairpin stabilized in the membrane by an arginine residue, similar to flaviviruses. A pair of histidine residues in the E2 ectodomain may participate in pH sensing. The proposed atomic models point to Cys987 in E2 as the site of disulfide bond linkage with E1 to form E1-E2 heterodimers. The membrane anchor models provide structural constraints for the disulfide bonding pattern and overall backbone conformation of the E1 ectodomain.
    Virology 04/2014; 454-455C(1):93-101. DOI:10.1016/j.virol.2014.02.015 · 3.32 Impact Factor
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    • "However, evidence of the extended intermediate has been largely indirect (Jiang et al., 1993; Miller et al., 2011; Pessi et al., 2012). Two recent reports have provided direct information about the extended intermediates in paramyxoviruses (Kim et al., 2011) and avian sarcoma leukosis virus (ASLV) (Cardone et al., 2012; Matsuyama et al., 2004). At present, no extended intermediate conformation from any virus has been characterized in high resolution. "
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    ABSTRACT: Viral fusion proteins undergo dramatic conformational transitions during membrane fusion. For viruses that enter through the endosome, these conformational rearrangements are typically pH sensitive. Here, we provide a comprehensive review of the molecular interactions that govern pH-dependent rearrangements and introduce a paradigm for electrostatic residue pairings that regulate progress through the viral fusion coordinate. Analysis of structural data demonstrates a significant role for side-chain protonation in triggering conformational change. To characterize this behavior, we identify two distinct residue pairings, which we define as Histidine-Cation (HisCat) and Anion-Anion (AniAni) interactions. These side-chain pairings destabilize a particular conformation via electrostatic repulsion through side-chain protonation. Furthermore, two energetic control mechanisms, thermodynamic and kinetic, regulate these structural transitions. This review expands on the current literature by identification of these residue clusters, discussion of data demonstrating their function, and speculation of how these residue pairings contribute to the energetic controls.
    Structure 07/2013; 21(7):1085-96. DOI:10.1016/j.str.2013.05.009 · 5.62 Impact Factor
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    ABSTRACT: The paramyxovirus family contains many common human pathogenic viruses, including measles, mumps, the parainfluenza viruses, respiratory syncytial virus, human metapneumovirus, and the zoonotic henipaviruses, Hendra and Nipah. While the expression of a type 1 fusion protein and a type 2 attachment protein is common to all paramyxoviruses, there is considerable variation in viral attachment, the activation and triggering of the fusion protein, and the process of viral entry. In this review, we discuss recent advances in the understanding of paramyxovirus F protein-mediated membrane fusion, an essential process in viral infectivity. We also review the role of the other surface glycoproteins in receptor binding and viral entry, and the implications for viral infection. Throughout, we concentrate on the commonalities and differences in fusion triggering and viral entry among the members of the family. Finally, we highlight key unanswered questions and how further studies can identify novel targets for the development of therapeutic treatments against these human pathogens.
    Viruses 04/2012; 4(4):613-36. DOI:10.3390/v4040613 · 3.35 Impact Factor
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