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PDBsum entry 3v6f
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Immune system
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PDB id
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3v6f
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References listed in PDB file
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Key reference
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Title
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Antigenic switching of hepatitis b virus by alternative dimerization of the capsid protein.
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Authors
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M.A.Dimattia,
N.R.Watts,
S.J.Stahl,
J.M.Grimes,
A.C.Steven,
D.I.Stuart,
P.T.Wingfield.
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Ref.
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Structure, 2013,
21,
133-142.
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PubMed id
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Abstract
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Chronic hepatitis B virus (HBV) infection afflicts millions worldwide with
cirrhosis and liver cancer. HBV e-antigen (HBeAg), a clinical marker for disease
severity, is a nonparticulate variant of the protein (core antigen, HBcAg) that
forms the building-blocks of capsids. HBeAg is not required for virion
production, but is implicated in establishing immune tolerance and chronic
infection. Here, we report the crystal structure of HBeAg, which clarifies how
the short N-terminal propeptide of HBeAg induces a radically altered mode of
dimerization relative to HBcAg (∼140° rotation), locked into place through
formation of intramolecular disulfide bridges. This structural switch precludes
capsid assembly and engenders a distinct antigenic repertoire, explaining why
the two antigens are cross-reactive at the T cell level (through sequence
identity) but not at the B cell level (through conformation). The structure
offers insight into how HBeAg may establish immune tolerance for HBcAg while
evading its robust immunogenicity.
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