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Zihe Rao - One of the best experts on this subject based on the ideXlab platform.
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crystal structure of severe acute respiratory syndrome coronaVirus Spike Protein fusion core
Journal of Biological Chemistry, 2004Co-Authors: Yanhui Xu, Zhiyong Lou, Hai Pang, Po Tien, George F. Gao, Yiwei Liu, Zihe RaoAbstract:Severe acute respiratory syndrome coronaVirus is a newly emergent Virus responsible for a recent outbreak of an atypical pneumonia. The coronaVirus Spike Protein, an enveloped glycoProtein essential for viral entry, belongs to the class I fusion Proteins and is characterized by the presence of two heptad repeat (HR) regions, HR1 and HR2. These two regions are understood to form a fusion-active conformation similar to those of other typical viral fusion Proteins. This hairpin structure likely juxtaposes the viral and cellular membranes, thus facilitating membrane fusion and subsequent viral entry. The fusion core Protein of severe acute respiratory syndrome coronaVirus Spike Protein was crystallized, and the structure was determined at 2.8 A of resolution. The fusion core is a six-helix bundle with three HR2 helices packed against the hydrophobic grooves on the surface of central coiled coil formed by three parallel HR1 helices in an oblique antiparallel manner. This structure shares significant similarity with the fusion core structure of mouse hepatitis Virus Spike Protein and other viral fusion Proteins, suggesting a conserved mechanism of membrane fusion. Drug discovery strategies aimed at inhibiting viral entry by blocking hairpin formation, which have been successfully used in human immunodeficiency Virus 1 inhibitor development, may be applicable to the inhibition of severe acute respiratory syndrome coronaVirus on the basis of structural information provided here. The relatively deep grooves on the surface of the central coiled coil will be a good target site for the design of viral fusion inhibitors.
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structural basis for coronaVirus mediated membrane fusion crystal structure of mouse hepatitis Virus Spike Protein fusion core
Journal of Biological Chemistry, 2004Co-Authors: Yiwei Liu, Zhiyong Lou, Hai Pang, Po Tien, George F. Gao, Lan Qin, Zhihong Bai, Zihe RaoAbstract:Abstract The surface transmembrane glycoProtein is responsible for mediating virion attachment to cell and subsequent Virus-cell membrane fusion. However, the molecular mechanisms for the viral entry of coronaViruses remain poorly understood. The crystal structure of the fusion core of mouse hepatitis Virus S Protein, which represents the first fusion core structure of any coronaVirus, reveals a central hydrophobic coiled coil trimer surrounded by three helices in an oblique, antiparallel manner. This structure shares significant similarity with both the low pH-induced conformation of influenza hemagglutinin and fusion core of HIV gp41, indicating that the structure represents a fusion-active state formed after several conformational changes. Our results also indicate that the mechanisms for the viral fusion of coronaViruses are similar to those of influenza Virus and HIV. The coiled coil structure has unique features, which are different from other viral fusion cores. Highly conserved heptad repeat 1 (HR1) and HR2 regions in coronaVirus Spike Proteins indicate a similar three-dimensional structure among these fusion cores and common mechanisms for the viral fusion. We have proposed the binding regions of HR1 and HR2 of other coronaViruses and a structure model of their fusion core based on our mouse hepatitis Virus fusion core structure and sequence alignment. Drug discovery strategies aimed at inhibiting viral entry by blocking hairpin formation may be applied to the inhibition of a number of emerging infectious diseases, including severe acute respiratory syndrome.
George F. Gao - One of the best experts on this subject based on the ideXlab platform.
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crystal structure of severe acute respiratory syndrome coronaVirus Spike Protein fusion core
Journal of Biological Chemistry, 2004Co-Authors: Yanhui Xu, Zhiyong Lou, Hai Pang, Po Tien, George F. Gao, Yiwei Liu, Zihe RaoAbstract:Severe acute respiratory syndrome coronaVirus is a newly emergent Virus responsible for a recent outbreak of an atypical pneumonia. The coronaVirus Spike Protein, an enveloped glycoProtein essential for viral entry, belongs to the class I fusion Proteins and is characterized by the presence of two heptad repeat (HR) regions, HR1 and HR2. These two regions are understood to form a fusion-active conformation similar to those of other typical viral fusion Proteins. This hairpin structure likely juxtaposes the viral and cellular membranes, thus facilitating membrane fusion and subsequent viral entry. The fusion core Protein of severe acute respiratory syndrome coronaVirus Spike Protein was crystallized, and the structure was determined at 2.8 A of resolution. The fusion core is a six-helix bundle with three HR2 helices packed against the hydrophobic grooves on the surface of central coiled coil formed by three parallel HR1 helices in an oblique antiparallel manner. This structure shares significant similarity with the fusion core structure of mouse hepatitis Virus Spike Protein and other viral fusion Proteins, suggesting a conserved mechanism of membrane fusion. Drug discovery strategies aimed at inhibiting viral entry by blocking hairpin formation, which have been successfully used in human immunodeficiency Virus 1 inhibitor development, may be applicable to the inhibition of severe acute respiratory syndrome coronaVirus on the basis of structural information provided here. The relatively deep grooves on the surface of the central coiled coil will be a good target site for the design of viral fusion inhibitors.
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structural basis for coronaVirus mediated membrane fusion crystal structure of mouse hepatitis Virus Spike Protein fusion core
Journal of Biological Chemistry, 2004Co-Authors: Yiwei Liu, Zhiyong Lou, Hai Pang, Po Tien, George F. Gao, Lan Qin, Zhihong Bai, Zihe RaoAbstract:Abstract The surface transmembrane glycoProtein is responsible for mediating virion attachment to cell and subsequent Virus-cell membrane fusion. However, the molecular mechanisms for the viral entry of coronaViruses remain poorly understood. The crystal structure of the fusion core of mouse hepatitis Virus S Protein, which represents the first fusion core structure of any coronaVirus, reveals a central hydrophobic coiled coil trimer surrounded by three helices in an oblique, antiparallel manner. This structure shares significant similarity with both the low pH-induced conformation of influenza hemagglutinin and fusion core of HIV gp41, indicating that the structure represents a fusion-active state formed after several conformational changes. Our results also indicate that the mechanisms for the viral fusion of coronaViruses are similar to those of influenza Virus and HIV. The coiled coil structure has unique features, which are different from other viral fusion cores. Highly conserved heptad repeat 1 (HR1) and HR2 regions in coronaVirus Spike Proteins indicate a similar three-dimensional structure among these fusion cores and common mechanisms for the viral fusion. We have proposed the binding regions of HR1 and HR2 of other coronaViruses and a structure model of their fusion core based on our mouse hepatitis Virus fusion core structure and sequence alignment. Drug discovery strategies aimed at inhibiting viral entry by blocking hairpin formation may be applied to the inhibition of a number of emerging infectious diseases, including severe acute respiratory syndrome.
Margaret Kielian - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of mutations inhibiting fusion and infection by semliki forest Virus
Journal of Cell Biology, 1996Co-Authors: Margaret Kielian, Matthew R Klimjack, Swati Ghosh, Wayne A DuffusAbstract:Semliki Forest Virus (SFV) infects cells by an acid-dependent membrane fusion reaction catalyzed by the Virus Spike Protein, a complex containing E1 and E2 transmembrane subunits. E1 carries the putative Virus fusion peptide, and mutations in this domain of the Spike Protein were previously shown to shift the pH threshold of cell-cell fusion (G91A), or block cell-cell fusion (G91D). We have used an SFV infectious clone to characterize Virus particles containing these mutations. In keeping with the previous Spike Protein results, G91A Virus showed limited secondary infection and an acid-shifted fusion threshold, while G91D Virus was noninfectious and inactive in both cell-cell and Virus-liposome fusion assays. During the low pH- induced SFV fusion reaction, the E1 subunit exposes new epitopes for monoclonal antibody (mAb) binding and forms an SDS-resistant homotrimer, the Virus associates hydrophobically with the target membrane, and fusion of the Virus and target membranes occurs. After low pH treatment, G91A Spike Proteins were shown to bind conformation-specific mAbs, associate with target liposome membranes, and form the E1 homotrimer. However, both G91A membrane association and homotrimer formation had an acid-shifted pH threshold and reduced efficiency compared to wt Virus. In contrast, studies of the fusion-defective G91D mutant showed that the Virus efficiently reacted with low pH as assayed by mAb binding and liposome association, but was essentially inactive in homotrimer formation. These results suggest that the G91D mutant is noninfectious due to a block in a late step in membrane fusion, separate from the initial reaction to low pH and interaction with the target membrane, and involving the lack of efficient formation of the E1 homotrimer.
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Mutagenesis of the putative fusion domain of the Semliki Forest Virus Spike Protein.
Journal of virology, 1991Co-Authors: P Levy-mintz, Margaret KielianAbstract:Semliki Forest Virus (SFV), an alphaVirus, infects cells via a low pH-triggered membrane fusion reaction that takes place within the cellular endocytic pathway. Fusion is mediated by the heterotrimeric Virus Spike Protein, which undergoes conformational changes upon exposure to low pH. The SFV E1 Spike subunit contains a hydrophobic domain of 23 amino acids that is highly conserved among alphaViruses. This region is also homologous to a domain of the rotaVirus outer capsid Protein VP4. Mutagenesis of an SFV Spike Protein cDNA was used to evaluate the role of the E1 domain in membrane fusion. Mutant Spike Proteins were expressed in COS cells and assayed for cell-cell fusion activity. Four mutant phenotypes were identified: (i) substitution of Gln for Lys-79 or Leu for Met-88 had no effect on Spike Protein fusion activity; (ii) substitution of Ala for Asp-75, Ala for Gly-83, or Ala for Gly-91 shifted the pH threshold of fusion to a more acidic range; (iii) mutation of Pro-86 to Asp, Gly-91 to Pro, or deletion of amino acids 83 to 92 resulted in retention of the E1 subunit within the endoplasmic reticulum; and (iv) substitution of Asp for Gly-91 completely blocked cell-cell fusion activity without affecting Spike Protein assembly or transport. These results argue that the conserved hydrophobic domain of SFV E1 is closely involved in membrane fusion and suggest that the homologous region in rotaVirus VP4 may be involved in the entry pathway of this nonenveloped Virus.
Yiwei Liu - One of the best experts on this subject based on the ideXlab platform.
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crystal structure of severe acute respiratory syndrome coronaVirus Spike Protein fusion core
Journal of Biological Chemistry, 2004Co-Authors: Yanhui Xu, Zhiyong Lou, Hai Pang, Po Tien, George F. Gao, Yiwei Liu, Zihe RaoAbstract:Severe acute respiratory syndrome coronaVirus is a newly emergent Virus responsible for a recent outbreak of an atypical pneumonia. The coronaVirus Spike Protein, an enveloped glycoProtein essential for viral entry, belongs to the class I fusion Proteins and is characterized by the presence of two heptad repeat (HR) regions, HR1 and HR2. These two regions are understood to form a fusion-active conformation similar to those of other typical viral fusion Proteins. This hairpin structure likely juxtaposes the viral and cellular membranes, thus facilitating membrane fusion and subsequent viral entry. The fusion core Protein of severe acute respiratory syndrome coronaVirus Spike Protein was crystallized, and the structure was determined at 2.8 A of resolution. The fusion core is a six-helix bundle with three HR2 helices packed against the hydrophobic grooves on the surface of central coiled coil formed by three parallel HR1 helices in an oblique antiparallel manner. This structure shares significant similarity with the fusion core structure of mouse hepatitis Virus Spike Protein and other viral fusion Proteins, suggesting a conserved mechanism of membrane fusion. Drug discovery strategies aimed at inhibiting viral entry by blocking hairpin formation, which have been successfully used in human immunodeficiency Virus 1 inhibitor development, may be applicable to the inhibition of severe acute respiratory syndrome coronaVirus on the basis of structural information provided here. The relatively deep grooves on the surface of the central coiled coil will be a good target site for the design of viral fusion inhibitors.
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structural basis for coronaVirus mediated membrane fusion crystal structure of mouse hepatitis Virus Spike Protein fusion core
Journal of Biological Chemistry, 2004Co-Authors: Yiwei Liu, Zhiyong Lou, Hai Pang, Po Tien, George F. Gao, Lan Qin, Zhihong Bai, Zihe RaoAbstract:Abstract The surface transmembrane glycoProtein is responsible for mediating virion attachment to cell and subsequent Virus-cell membrane fusion. However, the molecular mechanisms for the viral entry of coronaViruses remain poorly understood. The crystal structure of the fusion core of mouse hepatitis Virus S Protein, which represents the first fusion core structure of any coronaVirus, reveals a central hydrophobic coiled coil trimer surrounded by three helices in an oblique, antiparallel manner. This structure shares significant similarity with both the low pH-induced conformation of influenza hemagglutinin and fusion core of HIV gp41, indicating that the structure represents a fusion-active state formed after several conformational changes. Our results also indicate that the mechanisms for the viral fusion of coronaViruses are similar to those of influenza Virus and HIV. The coiled coil structure has unique features, which are different from other viral fusion cores. Highly conserved heptad repeat 1 (HR1) and HR2 regions in coronaVirus Spike Proteins indicate a similar three-dimensional structure among these fusion cores and common mechanisms for the viral fusion. We have proposed the binding regions of HR1 and HR2 of other coronaViruses and a structure model of their fusion core based on our mouse hepatitis Virus fusion core structure and sequence alignment. Drug discovery strategies aimed at inhibiting viral entry by blocking hairpin formation may be applied to the inhibition of a number of emerging infectious diseases, including severe acute respiratory syndrome.
David Holcman - One of the best experts on this subject based on the ideXlab platform.
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Stochastic Model of Acidification, Activation of Hemagglutinin and Escape of Influenza Viruses from an Endosome
Frontiers in Physics, 2017Co-Authors: Thibault Lagache, Christian Sieben, Tim Meyer, Andreas Herrmann, David HolcmanAbstract:Influenza Viruses enter the cell inside an endosome. During the endosomal journey, acidification triggers a conformational change of the Virus Spike Protein hemagglutinin (HA) that results in escape of the viral genome from the endosome into the cytoplasm. It is still unclear how the interplay between acidification and HA conformation changes affects the kinetics of the viral endosomal escape. We develop here a stochastic model to estimate the change of conformation of HAs inside the endosome nanodomain. Using a Markov process, we model the arrival of protons to HA binding sites and compute the kinetics of their accumulation. We compute the Mean First Passage Time (MFPT) of the number of HA bound sites to a threshold, which is used to estimate the HA activation rate for a given pH concentration. The present analysis reveals that HA proton binding sites possess a high chemical barrier, ensuring a stability of the Spike Protein at sub-acidic pH. We predict that activating more than 3 adjacent HAs is necessary to trigger endosomal fusion and this configuration prevents premature release of Viruses from early endosomes
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Stochastic Model of Acidification, Activation of Hemagglutinin and Escape of Influenza Viruses from an Endosome
Frontiers in Physics, 2017Co-Authors: Thibault Lagache, Christian Sieben, Tim Meyer, Andreas Herrmann, David HolcmanAbstract:Influenza Viruses enter the cell inside an endosome. During the endosomal journey, acidification triggers a conformational change of the Virus Spike Protein hemagglutinin (HA) that results in escape of the viral genome from the endosome into the cytoplasm. It is still unclear how the interplay between acidification and HA conformation changes affects the kinetics of the viral endosomal escape. We develop here a stochastic model to estimate the change of conformation of HAs inside the endosome nanodomain. Using a Markov process, we model the arrival of protons to HA binding sites and compute the kinetics of their accumulation. We compute the Mean First Passage Time (MFPT) of the number of HA bound sites to a threshold, which is used to estimate the HA activation rate for a given pH (i.e. proton concentration). The present analysis reveals that HA proton binding sites possess a high chemical barrier, ensuring a stability of the Spike Protein at sub-acidic pH. We predict that activating more than 3 adjacent HAs is necessary to trigger endosomal fusion and this configuration prevents premature release of Viruses from early endosomes.
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Stochastic model of endosomal escape of Influenza Virus
arXiv: Subcellular Processes, 2015Co-Authors: Thibault Lagache, Christian Sieben, Tim Meyer, Andreas Herrmann, David HolcmanAbstract:Influenza Viruses enter a cell via endocytosis after binding to the surface. During the endosomal journey, acidification triggers a conformational change of the Virus Spike Protein hemagglutinin (HA) that results in escape of the viral genome from the endosome to the cytoplasm. A quantitative understanding of the processes involved in HA mediated fusion with the endosome is still missing. We develop here a stochastic model to estimate the change of conformation of HAs inside the endosome nanodomain. Using a Markov-jump process to model the arrival of protons to HA binding sites, we compute the kinetics of their accumulation and the mean first time for HAs to be activated. This analysis reveals that HA proton binding sites possess a high chemical barrier, ensuring a stability of the Spike Protein at sub-acidic pH. Finally, we predict that activating more than 3 adjacent HAs is necessary to prevent a premature fusion.
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Influenza Virus Hemagglutinin Delays Endosomal Acidification - a Strategy for Successful Delivery of the Viral Genome?
Biophysical Journal, 2012Co-Authors: Christian Sieben, Thibault Lagache, David Holcman, Andreas HerrmannAbstract:Upon endocytic uptake of influenza Virus, acidification of the endosomal lumen triggers a conformational change of the Virus Spike Protein hemagglutinin (HA) leading to fusion between the endosomal and the viral membrane. For efficient infection, release of the viral genome favorably occurs in the vicinity of the nucleus to prevent lysosomal degradation of the viral RNA and activation of the cellular antiviral response. How influenza Viruses ensure optimal duration of endosomal residence to avoid premature as well as delayed fusion and release of the genome is not understood.The tight packing of HA in the viral envelope represents a remarkably high intra-endosomal Protein concentration with high buffering potential for incoming protons. By using pH sensitive fluorescent markers we could show for the first time that the presence of a Virus inside an endosome drastically slows down the acidification kinetics. We investigated the effect of cytoskeletal inhibitors on Virus fusion and infection using a combination of single Virus tracking and an intracellular fusion assay. In control cells, fusion mostly occurs in the perinuclear region. Inhibition of endosomal transport along microtubules by nocodazole did not change the numbers of fusion events, but randomized their localization within the cell. Interestingly, this dislocation correlates with strongly reduced infection efficiency, confirming that the site of Virus-endosome fusion indeed plays an important role in the delivery of the viral genome.Taken together, our results demonstrate that influenza Virus HA delays the endosomal acidification to ensure timely as well as locally optimal release of its genome. This suggests a general function of the high-density packing of Spike Proteins that is characteristic of enveloped Viruses infecting via the endocytic route.
