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Characterization of monomeric intermediates during VSV glycoprotein structural transition.

Albertini AA, Mérigoux C, Libersou S, Madiona K, Bressanelli S, Roche S, Lepault J, Melki R, Vachette P, Gaudin Y - PLoS Pathog. (2012)

Bottom Line: The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases.Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification.We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche de Gif, Laboratoire de Virologie Moléculaire et Structurale, CNRS (UPR 3296), Gif sur Yvette, France.

ABSTRACT
Entry of enveloped viruses requires fusion of viral and cellular membranes, driven by conformational changes of viral glycoproteins. Crystal structures provide static pictures of pre- and post-fusion conformations of these proteins but the transition pathway remains elusive. Here, using several biophysical techniques, including analytical ultracentrifugation, circular dichroïsm, electron microscopy and small angle X-ray scattering, we have characterized the low-pH-induced fusogenic structural transition of a soluble form of vesicular stomatitis virus (VSV) glycoprotein G ectodomain (G(th), aa residues 1-422, the fragment that was previously crystallized). While the post-fusion trimer is the major species detected at low pH, the pre-fusion trimer is not detected in solution. Rather, at high pH, G(th) is a flexible monomer that explores a large conformational space. The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases. Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification. Solution studies are complemented by electron micrographs of negatively stained viral particles in which monomeric ectodomains of G are observed at the viral surface at both pH 7.5 and pH 6.7. We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.

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Electron microscopy on negatively stained Gth at pH 7.5, pH 6.7 and pH 5.7.(A) At pH 7.5, no oligomer of Gth is detected and a definite molecular shape cannot be identified. (B) At pH 6.7 a few Gth assemblies can be detected. (C) At pH 5.7 Gth trimers are observed assembled either in lattice via lateral interactions or in rosette-like assemblies. Protein concentration was 0.1 mg/mL for all 3 samples. The scale bar is for 100 nm. (D) Close up view of Gth rosettes observed at pH 6.7 and 5.7. Notice the differences in the aspect of the protein assemblies. The scale bar is for 20 nm.
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ppat-1002556-g006: Electron microscopy on negatively stained Gth at pH 7.5, pH 6.7 and pH 5.7.(A) At pH 7.5, no oligomer of Gth is detected and a definite molecular shape cannot be identified. (B) At pH 6.7 a few Gth assemblies can be detected. (C) At pH 5.7 Gth trimers are observed assembled either in lattice via lateral interactions or in rosette-like assemblies. Protein concentration was 0.1 mg/mL for all 3 samples. The scale bar is for 100 nm. (D) Close up view of Gth rosettes observed at pH 6.7 and 5.7. Notice the differences in the aspect of the protein assemblies. The scale bar is for 20 nm.

Mentions: We analyzed the various species previously identified by AUC and SAXS using electron microscopy and negative staining (Figure 6).


Characterization of monomeric intermediates during VSV glycoprotein structural transition.

Albertini AA, Mérigoux C, Libersou S, Madiona K, Bressanelli S, Roche S, Lepault J, Melki R, Vachette P, Gaudin Y - PLoS Pathog. (2012)

Electron microscopy on negatively stained Gth at pH 7.5, pH 6.7 and pH 5.7.(A) At pH 7.5, no oligomer of Gth is detected and a definite molecular shape cannot be identified. (B) At pH 6.7 a few Gth assemblies can be detected. (C) At pH 5.7 Gth trimers are observed assembled either in lattice via lateral interactions or in rosette-like assemblies. Protein concentration was 0.1 mg/mL for all 3 samples. The scale bar is for 100 nm. (D) Close up view of Gth rosettes observed at pH 6.7 and 5.7. Notice the differences in the aspect of the protein assemblies. The scale bar is for 20 nm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3285605&req=5

ppat-1002556-g006: Electron microscopy on negatively stained Gth at pH 7.5, pH 6.7 and pH 5.7.(A) At pH 7.5, no oligomer of Gth is detected and a definite molecular shape cannot be identified. (B) At pH 6.7 a few Gth assemblies can be detected. (C) At pH 5.7 Gth trimers are observed assembled either in lattice via lateral interactions or in rosette-like assemblies. Protein concentration was 0.1 mg/mL for all 3 samples. The scale bar is for 100 nm. (D) Close up view of Gth rosettes observed at pH 6.7 and 5.7. Notice the differences in the aspect of the protein assemblies. The scale bar is for 20 nm.
Mentions: We analyzed the various species previously identified by AUC and SAXS using electron microscopy and negative staining (Figure 6).

Bottom Line: The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases.Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification.We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche de Gif, Laboratoire de Virologie Moléculaire et Structurale, CNRS (UPR 3296), Gif sur Yvette, France.

ABSTRACT
Entry of enveloped viruses requires fusion of viral and cellular membranes, driven by conformational changes of viral glycoproteins. Crystal structures provide static pictures of pre- and post-fusion conformations of these proteins but the transition pathway remains elusive. Here, using several biophysical techniques, including analytical ultracentrifugation, circular dichroïsm, electron microscopy and small angle X-ray scattering, we have characterized the low-pH-induced fusogenic structural transition of a soluble form of vesicular stomatitis virus (VSV) glycoprotein G ectodomain (G(th), aa residues 1-422, the fragment that was previously crystallized). While the post-fusion trimer is the major species detected at low pH, the pre-fusion trimer is not detected in solution. Rather, at high pH, G(th) is a flexible monomer that explores a large conformational space. The monomeric population exhibits a marked pH-dependence and adopts more elongated conformations when pH decreases. Furthermore, large relative movements of domains are detected in absence of significant secondary structure modification. Solution studies are complemented by electron micrographs of negatively stained viral particles in which monomeric ectodomains of G are observed at the viral surface at both pH 7.5 and pH 6.7. We propose that the monomers are intermediates during the conformational change and thus that VSV G trimers dissociate at the viral surface during the structural transition.

Show MeSH
Related in: MedlinePlus