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Biophysical characterization and membrane interaction of the two fusion loops of glycoprotein B from herpes simplex type I virus.

Falanga A, Tarallo R, Vitiello G, Vitiello M, Perillo E, Cantisani M, D'Errico G, Galdiero M, Galdiero S - PLoS ONE (2012)

Bottom Line: Here, we report the first biophysical study on the two fusion peptides of gB, with a particular focus on the effects determined by both peptides on lipid bilayers of various compositions.The two fusion loops constitute a structural subdomain wherein key hydrophobic amino acids form a ridge that is supported on both sides by charged residues.When used together the two fusion loops have the ability to significantly destabilize the target membrane bilayer, notwithstanding their low bilayer penetration when used separately.

View Article: PubMed Central - PubMed

Affiliation: Division of Biostructures, Department of Biological Sciences, University of Naples Federico II, Napoli, Italy.

ABSTRACT
The molecular mechanism of entry of herpesviruses requires a multicomponent fusion system. Cell invasion by Herpes simplex virus (HSV) requires four virally encoded glycoproteins: namely gD, gB and gH/gL. The role of gB has remained elusive until recently when the crystal structure of HSV-1 gB became available and the fusion potential of gB was clearly demonstrated. Although much information on gB structure/function relationship has been gathered in recent years, the elucidation of the nature of the fine interactions between gB fusion loops and the membrane bilayer may help to understand the precise molecular mechanism behind herpesvirus-host cell membrane fusion. Here, we report the first biophysical study on the two fusion peptides of gB, with a particular focus on the effects determined by both peptides on lipid bilayers of various compositions. The two fusion loops constitute a structural subdomain wherein key hydrophobic amino acids form a ridge that is supported on both sides by charged residues. When used together the two fusion loops have the ability to significantly destabilize the target membrane bilayer, notwithstanding their low bilayer penetration when used separately. These data support the model of gB fusion loops insertion into cholesterol enriched membranes.

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Related in: MedlinePlus

Quenching of tryptophan/tyrosines by Acrylamide.Stern-Volmer plots of acrylamide quenching of HB168–186 and HB254–270 in buffer (closed symbols) and in LUVs (open symbols).
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pone-0032186-g006: Quenching of tryptophan/tyrosines by Acrylamide.Stern-Volmer plots of acrylamide quenching of HB168–186 and HB254–270 in buffer (closed symbols) and in LUVs (open symbols).

Mentions: The observed changes in the characteristics of the tryptophan/tyrosine emission upon binding of peptides HB168–186 and HB254–270 to lipid vesicles indicate their insertion into the hydrophobic region of the bilayers. We also studied the accessibility of the tryptophan/tyrosine residues of membrane-bound peptides towards acrylamide, a neutral, water-soluble, highly efficient quenching molecule, which is unable to penetrate into the hydrophobic core of the lipid bilayer. The more deeply a tryptophan/tyrosine residue is buried, the less strongly it can be quenched by acrylamide. Stern-Volmer plots for the quenching of tryptophan by acrylamide, recorded in the absence and presence of lipid vesicles, are depicted in Figure 6. Fluorescence of tryptophan/tyrosine decreased in a concentration-dependent manner by the addition of acrylamide to the peptide solution both in the absence and presence of liposomes, without other effects on the spectra. However, we can observe a substantial difference between the two peptides. In the presence of liposomes, a great decrease in fluorescence intensity was evident for HB254–270, thus revealing that tyrosine residues are less accessible to the quencher in the presence of LUVs. In fact, the values for Ksv were lower (Table 3) in LUVs, suggesting that tyrosines were more buried in the bilayers, becoming more inaccessible for quenching by acrylamide. From Figure 6, it is evident that we can observe for the peptide HB168–186 a low accessibility to the quencher both in absence and presence of liposomes, indicating that the peptide has a significant tendency to aggregate also in an aqueous solution.


Biophysical characterization and membrane interaction of the two fusion loops of glycoprotein B from herpes simplex type I virus.

Falanga A, Tarallo R, Vitiello G, Vitiello M, Perillo E, Cantisani M, D'Errico G, Galdiero M, Galdiero S - PLoS ONE (2012)

Quenching of tryptophan/tyrosines by Acrylamide.Stern-Volmer plots of acrylamide quenching of HB168–186 and HB254–270 in buffer (closed symbols) and in LUVs (open symbols).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3285657&req=5

pone-0032186-g006: Quenching of tryptophan/tyrosines by Acrylamide.Stern-Volmer plots of acrylamide quenching of HB168–186 and HB254–270 in buffer (closed symbols) and in LUVs (open symbols).
Mentions: The observed changes in the characteristics of the tryptophan/tyrosine emission upon binding of peptides HB168–186 and HB254–270 to lipid vesicles indicate their insertion into the hydrophobic region of the bilayers. We also studied the accessibility of the tryptophan/tyrosine residues of membrane-bound peptides towards acrylamide, a neutral, water-soluble, highly efficient quenching molecule, which is unable to penetrate into the hydrophobic core of the lipid bilayer. The more deeply a tryptophan/tyrosine residue is buried, the less strongly it can be quenched by acrylamide. Stern-Volmer plots for the quenching of tryptophan by acrylamide, recorded in the absence and presence of lipid vesicles, are depicted in Figure 6. Fluorescence of tryptophan/tyrosine decreased in a concentration-dependent manner by the addition of acrylamide to the peptide solution both in the absence and presence of liposomes, without other effects on the spectra. However, we can observe a substantial difference between the two peptides. In the presence of liposomes, a great decrease in fluorescence intensity was evident for HB254–270, thus revealing that tyrosine residues are less accessible to the quencher in the presence of LUVs. In fact, the values for Ksv were lower (Table 3) in LUVs, suggesting that tyrosines were more buried in the bilayers, becoming more inaccessible for quenching by acrylamide. From Figure 6, it is evident that we can observe for the peptide HB168–186 a low accessibility to the quencher both in absence and presence of liposomes, indicating that the peptide has a significant tendency to aggregate also in an aqueous solution.

Bottom Line: Here, we report the first biophysical study on the two fusion peptides of gB, with a particular focus on the effects determined by both peptides on lipid bilayers of various compositions.The two fusion loops constitute a structural subdomain wherein key hydrophobic amino acids form a ridge that is supported on both sides by charged residues.When used together the two fusion loops have the ability to significantly destabilize the target membrane bilayer, notwithstanding their low bilayer penetration when used separately.

View Article: PubMed Central - PubMed

Affiliation: Division of Biostructures, Department of Biological Sciences, University of Naples Federico II, Napoli, Italy.

ABSTRACT
The molecular mechanism of entry of herpesviruses requires a multicomponent fusion system. Cell invasion by Herpes simplex virus (HSV) requires four virally encoded glycoproteins: namely gD, gB and gH/gL. The role of gB has remained elusive until recently when the crystal structure of HSV-1 gB became available and the fusion potential of gB was clearly demonstrated. Although much information on gB structure/function relationship has been gathered in recent years, the elucidation of the nature of the fine interactions between gB fusion loops and the membrane bilayer may help to understand the precise molecular mechanism behind herpesvirus-host cell membrane fusion. Here, we report the first biophysical study on the two fusion peptides of gB, with a particular focus on the effects determined by both peptides on lipid bilayers of various compositions. The two fusion loops constitute a structural subdomain wherein key hydrophobic amino acids form a ridge that is supported on both sides by charged residues. When used together the two fusion loops have the ability to significantly destabilize the target membrane bilayer, notwithstanding their low bilayer penetration when used separately. These data support the model of gB fusion loops insertion into cholesterol enriched membranes.

Show MeSH
Related in: MedlinePlus