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PDBsum entry 1hc9
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Toxin/peptide
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PDB id
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1hc9
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Contents |
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74 a.a.
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74 a.a.
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13 a.a.
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12 a.a.
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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The binding site of acetylcholine receptor as visualized in the X-Ray structure of a complex between alpha-Bungarotoxin and a mimotope peptide.
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Authors
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M.Harel,
R.Kasher,
A.Nicolas,
J.M.Guss,
M.Balass,
M.Fridkin,
A.B.Smit,
K.Brejc,
T.K.Sixma,
E.Katchalski-Katzir,
J.L.Sussman,
S.Fuchs.
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Ref.
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Neuron, 2001,
32,
265-275.
[DOI no: ]
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PubMed id
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Abstract
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We have determined the crystal structure at 1.8 A resolution of a complex of
alpha-bungarotoxin with a high affinity 13-residue peptide that is homologous to
the binding region of the alpha subunit of acetylcholine receptor. The peptide
fits snugly to the toxin and adopts a beta hairpin conformation. The structures
of the bound peptide and the homologous loop of acetylcholine binding protein, a
soluble analog of the extracellular domain of acetylcholine receptor, are
remarkably similar. Their superposition indicates that the toxin wraps around
the receptor binding site loop, and in addition, binds tightly at the interface
of two of the receptor subunits where it inserts a finger into the ligand
binding site, thus blocking access to the acetylcholine binding site and
explaining its strong antagonistic activity.
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Figure 6.
Figure 6. A Stereo View of the Combined Model of α-BTX-HAP
(Red) and AChBP Structure with Subunit A in Green and Subunit B
in Yellow Showing the Insertion of Loop 2 of the Toxin into the
Interface of the Two SubunitsThe positively charged HEPES
molecule (black stick figure) shows the location of the
acetylcholine binding site and the blockage of passage to this
site caused by the binding of the toxin. The HAP, which overlaps
the 182–193 loop of AChBP, is shown in blue
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Figure 7.
Figure 7. The Combined Model of the AChBP Pentamer with
Five Copies of α-BTX (Red) Bound to It, as Viewed down the
5-Fold Axis of the Pentamer
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The above figures are
reprinted
by permission from Cell Press:
Neuron
(2001,
32,
265-275)
copyright 2001.
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