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PDBsum entry 3fd4
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Viral protein
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PDB id
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3fd4
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References listed in PDB file
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Key reference
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Title
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Structure of epstein-Barr virus glycoprotein 42 suggests a mechanism for triggering receptor-Activated virus entry.
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Authors
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A.N.Kirschner,
J.Sorem,
R.Longnecker,
T.S.Jardetzky.
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Ref.
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Structure, 2009,
17,
223-233.
[DOI no: ]
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PubMed id
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Abstract
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Epstein-Barr virus requires glycoproteins gH/gL, gB, and gp42 to fuse its lipid
envelope with B cells. Gp42 is a type II membrane protein consisting of a
flexible N-terminal region, which binds gH/gL, and a C-terminal lectin-like
domain that binds to the B-cell entry receptor human leukocyte antigen (HLA)
class II. Gp42 triggers membrane fusion after HLA binding, a process that
requires simultaneous binding to gH/gL and a functional hydrophobic pocket in
the lectin domain adjacent to the HLA binding site. Here we present the
structure of gp42 in its unbound form. Comparisons to the previously determined
structure of a gp42:HLA complex reveals additional N-terminal residues forming
part of the gH/gL binding site and structural changes in the receptor binding
domain. Although the core of the lectin domain remains similar, significant
shifts in two loops and an alpha helix bordering the essential hydrophobic
pocket suggest a structural mechanism for triggering fusion.
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Figure 1.
Figure 1. Two Gp42 Molecules in the Asymmetric Unit
Ribbon diagrams of the two gp42 molecules in the asymmetric unit
in side (A) and top (B) views, colored from blue to red starting
at the N terminus. The N and C termini of each chain are marked.
Molecule B has a longer N terminus (starting at residue 76) than
molecule A (starting at residue 82). Both N termini form
extended regions heading away from the C-terminal C-type lectin
domain (CTLD). The broad hydrophobic pockets are indicated in
(B).
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Figure 3.
Figure 3. Residues 87–93 Pack Identically into
Symmetry-Related HLA Binding Sites
The gp42 N-terminal
residues that are immediately proximal to the CTLD extend
similarly in the two copies of the gp42 molecules in the
asymmetric unit and make identical packing interactions with the
HLA binding site of a neighboring molecule.
(A) The overlay
of the two gp42 molecules of the asymmetric unit is shown in
beige, with the N-terminal residues in yellow stick
representation that form this packing interaction with the
neighboring gp42 (blue). The HLA binding site is indicated and
the corresponding residues are shown as sticks.
(B) A
zoomed-in view of this packing interaction is shown, along with
the packing of residue F88 against hydrophobic HLA binding
residues.
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The above figures are
reprinted
by permission from Cell Press:
Structure
(2009,
17,
223-233)
copyright 2009.
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