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Structure of the core ectodomain of the hepatitis C virus envelope glycoprotein 2.

Khan AG, Whidby J, Miller MT, Scarborough H, Zatorski AV, Cygan A, Price AA, Yost SA, Bohannon CD, Jacob J, Grakoui A, Marcotrigiano J - Nature (2014)

Bottom Line: Sheet A has an IgG-like fold that is commonly found in viral and cellular proteins, whereas sheet B represents a novel fold.Solution-based studies demonstrate that the full-length E2 ectodomain has a similar globular architecture and does not undergo significant conformational or oligomeric rearrangements on exposure to low pH.These results provide unprecedented insights into HCV entry and will assist in developing an HCV vaccine and new inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, 679 Hoes Lane West, Piscataway, New Jersey 08854, USA.

ABSTRACT
Hepatitis C virus (HCV) is a significant public health concern with approximately 160 million people infected worldwide. HCV infection often results in chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. No vaccine is available and current therapies are effective against some, but not all, genotypes. HCV is an enveloped virus with two surface glycoproteins (E1 and E2). E2 binds to the host cell through interactions with scavenger receptor class B type I (SR-BI) and CD81, and serves as a target for neutralizing antibodies. Little is known about the molecular mechanism that mediates cell entry and membrane fusion, although E2 is predicted to be a class II viral fusion protein. Here we describe the structure of the E2 core domain in complex with an antigen-binding fragment (Fab) at 2.4 Å resolution. The E2 core has a compact, globular domain structure, consisting mostly of β-strands and random coil with two small α-helices. The strands are arranged in two, perpendicular sheets (A and B), which are held together by an extensive hydrophobic core and disulphide bonds. Sheet A has an IgG-like fold that is commonly found in viral and cellular proteins, whereas sheet B represents a novel fold. Solution-based studies demonstrate that the full-length E2 ectodomain has a similar globular architecture and does not undergo significant conformational or oligomeric rearrangements on exposure to low pH. Thus, the IgG-like fold is the only feature that E2 shares with class II membrane fusion proteins. These results provide unprecedented insights into HCV entry and will assist in developing an HCV vaccine and new inhibitors.

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Ab initio SAXS envelopes of E2 core, eE2ΔHVR1 and eE2SAXS envelopes of glycosylated E2 core (a), eE2 (b), eE2ΔHVR1 (c), and eE2ΔHVR1 in complex with CD81-LEL (d). The E2 core domain structure has been fitted into a and b. e, Superposition of the SAXS envelopes of eE2ΔHVR1 alone (c) and in complex with CD81-LEL (d), highlighting the approximate position of CD81-LEL.
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Figure 9: Ab initio SAXS envelopes of E2 core, eE2ΔHVR1 and eE2SAXS envelopes of glycosylated E2 core (a), eE2 (b), eE2ΔHVR1 (c), and eE2ΔHVR1 in complex with CD81-LEL (d). The E2 core domain structure has been fitted into a and b. e, Superposition of the SAXS envelopes of eE2ΔHVR1 alone (c) and in complex with CD81-LEL (d), highlighting the approximate position of CD81-LEL.

Mentions: Similar to the flavivirus and pestivirus glycoproteins, the HCV E2 core secondary structure consists of predominantly beta sheets and random coil. However, E2 core is a monomer with a compact globular shape, in contrast to the extended structures reported in other viruses. Solution-based small angle X-ray scattering (SAXS) was used to correlate the crystallographic core domain structure with fully glycosylated eE2 and various fragments. The ab initio SAXS envelopes of E2 core and eE2 are similar with approximately the same radius of gyration (Rg) (Fig. 2a-b and Extended Data Table 2). Glycosylation, which is missing in the E2 core crystal structure, represents roughly a third of the mass and accounts for the unmodeled areas of the envelopes. Interestingly, neither the Rg nor the elution profiles on SEC for fully glycosylated eE2 and E2 core changed significantly at pH 5.0 (Extended Data Fig. 6a-b). These results suggest that unlike class II membrane fusion proteins, E2 does not undergo significant structural rearrangements upon exposure to low pH.


Structure of the core ectodomain of the hepatitis C virus envelope glycoprotein 2.

Khan AG, Whidby J, Miller MT, Scarborough H, Zatorski AV, Cygan A, Price AA, Yost SA, Bohannon CD, Jacob J, Grakoui A, Marcotrigiano J - Nature (2014)

Ab initio SAXS envelopes of E2 core, eE2ΔHVR1 and eE2SAXS envelopes of glycosylated E2 core (a), eE2 (b), eE2ΔHVR1 (c), and eE2ΔHVR1 in complex with CD81-LEL (d). The E2 core domain structure has been fitted into a and b. e, Superposition of the SAXS envelopes of eE2ΔHVR1 alone (c) and in complex with CD81-LEL (d), highlighting the approximate position of CD81-LEL.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4126800&req=5

Figure 9: Ab initio SAXS envelopes of E2 core, eE2ΔHVR1 and eE2SAXS envelopes of glycosylated E2 core (a), eE2 (b), eE2ΔHVR1 (c), and eE2ΔHVR1 in complex with CD81-LEL (d). The E2 core domain structure has been fitted into a and b. e, Superposition of the SAXS envelopes of eE2ΔHVR1 alone (c) and in complex with CD81-LEL (d), highlighting the approximate position of CD81-LEL.
Mentions: Similar to the flavivirus and pestivirus glycoproteins, the HCV E2 core secondary structure consists of predominantly beta sheets and random coil. However, E2 core is a monomer with a compact globular shape, in contrast to the extended structures reported in other viruses. Solution-based small angle X-ray scattering (SAXS) was used to correlate the crystallographic core domain structure with fully glycosylated eE2 and various fragments. The ab initio SAXS envelopes of E2 core and eE2 are similar with approximately the same radius of gyration (Rg) (Fig. 2a-b and Extended Data Table 2). Glycosylation, which is missing in the E2 core crystal structure, represents roughly a third of the mass and accounts for the unmodeled areas of the envelopes. Interestingly, neither the Rg nor the elution profiles on SEC for fully glycosylated eE2 and E2 core changed significantly at pH 5.0 (Extended Data Fig. 6a-b). These results suggest that unlike class II membrane fusion proteins, E2 does not undergo significant structural rearrangements upon exposure to low pH.

Bottom Line: Sheet A has an IgG-like fold that is commonly found in viral and cellular proteins, whereas sheet B represents a novel fold.Solution-based studies demonstrate that the full-length E2 ectodomain has a similar globular architecture and does not undergo significant conformational or oligomeric rearrangements on exposure to low pH.These results provide unprecedented insights into HCV entry and will assist in developing an HCV vaccine and new inhibitors.

View Article: PubMed Central - PubMed

Affiliation: Center for Advanced Biotechnology and Medicine, Department of Chemistry and Chemical Biology, Rutgers University, 679 Hoes Lane West, Piscataway, New Jersey 08854, USA.

ABSTRACT
Hepatitis C virus (HCV) is a significant public health concern with approximately 160 million people infected worldwide. HCV infection often results in chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. No vaccine is available and current therapies are effective against some, but not all, genotypes. HCV is an enveloped virus with two surface glycoproteins (E1 and E2). E2 binds to the host cell through interactions with scavenger receptor class B type I (SR-BI) and CD81, and serves as a target for neutralizing antibodies. Little is known about the molecular mechanism that mediates cell entry and membrane fusion, although E2 is predicted to be a class II viral fusion protein. Here we describe the structure of the E2 core domain in complex with an antigen-binding fragment (Fab) at 2.4 Å resolution. The E2 core has a compact, globular domain structure, consisting mostly of β-strands and random coil with two small α-helices. The strands are arranged in two, perpendicular sheets (A and B), which are held together by an extensive hydrophobic core and disulphide bonds. Sheet A has an IgG-like fold that is commonly found in viral and cellular proteins, whereas sheet B represents a novel fold. Solution-based studies demonstrate that the full-length E2 ectodomain has a similar globular architecture and does not undergo significant conformational or oligomeric rearrangements on exposure to low pH. Thus, the IgG-like fold is the only feature that E2 shares with class II membrane fusion proteins. These results provide unprecedented insights into HCV entry and will assist in developing an HCV vaccine and new inhibitors.

Show MeSH
Related in: MedlinePlus