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PDBsum entry 1kfh
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Contents |
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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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Nmr structural analysis of alpha-Bungarotoxin and its complex with the principal alpha-Neurotoxin-Binding sequence on the alpha 7 subunit of a neuronal nicotinic acetylcholine receptor.
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Authors
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L.Moise,
A.Piserchio,
V.J.Basus,
E.Hawrot.
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Ref.
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J Biol Chem, 2002,
277,
12406-12417.
[DOI no: ]
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PubMed id
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Abstract
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We report a new, higher resolution NMR structure of alpha-bungarotoxin that
defines the structure-determining disulfide core and beta-sheet regions. We
further report the NMR structure of the stoichiometric complex formed between
alpha-bungarotoxin and a recombinantly expressed 19-mer peptide
((178)IPGKRTESFYECCKEPYPD(196)) derived from the alpha7 subunit of the chick
neuronal nicotinic acetylcholine receptor. A comparison of these two structures
reveals binding-induced stabilization of the flexible tip of finger II in
alpha-bungarotoxin. The conformational rearrangements in the toxin create an
extensive binding surface involving both sides of the alpha7 19-mer hairpin-like
structure. At the contact zone, Ala(7), Ser(9), and Ile(11) in finger I and
Arg(36), Lys(38), Val(39), and Val(40) in finger II of alpha-bungarotoxin
interface with Phe(186), Tyr(187), Glu(188), and Tyr(194) in the alpha7 19-mer
underscoring the importance of receptor aromatic residues as critical
neurotoxin-binding determinants. Superimposing the structure of the complex onto
that of the acetylcholine-binding protein (1I9B), a soluble homologue of the
extracellular domain of the alpha7 receptor, places alpha-bungarotoxin at the
peripheral surface of the inter-subunit interface occluding the agonist-binding
site. The disulfide-rich core of alpha-bungarotoxin is suggested to be tilted in
the direction of the membrane surface with finger II extending into the proposed
ligand-binding cavity.
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Figure 4.
Fig. 4. Stereo view of the  7
19-mer·Bgtx complex. Ten NMR-derived backbone traces of
Bgtx (blue) and the 7 19-mer
(red) are superimposed. N-terminal residues 178-184 of the 7 19-mer
are unconstrained and were removed in this figure. For
orientation, the N termini of Bgtx and the 7 19-mer,
as presented, are colored black. The C-terminal tail of Bgtx
(residues 69-74) is colored green for clarity. The figure was
prepared using the program MOLMOL (53).
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Figure 9.
Fig. 9. Model of Bgtx bound to the nAChR. The structured
region of the 7 19-mer
(Ser185-Tyr194) was superimposed onto the corresponding region
of the AChBP (Val183-Tyr192) to model the orientation of Bgtx
relative to the nAChR. The most representative structure from
the 7
19-mer·Bgtx ensemble, as calculated by NMRCLUST (82), was
chosen for superposition. A, superposition of backbone atoms of
7
19-mer(Ser185-Tyr194) in blue and AChBP(Val183-Tyr192) in red.
The first of the adjacent cysteines is green in both segments.
B, ribbon diagram of Bgtx at the subunit interface. Two adjacent
subunits of the AChBP pentamer are shown with the  -sheet in
blue on the plus side and yellow on the minus side. Bgtx,
between the subunits, is in magenta. C, global view of the
predicted Bgtx-nAChR interaction. A surface model of the AChBP
is shown with each subunit colored differently. This view of the
AChBP is perpendicular to the 5-fold axis with the synaptic side
on top and membrane side below. Bgtx is shown as a red stick
model with the unstructured C-terminal tail removed. The 7 19-mer is
not shown for clarity. The  1 angles of
Gln167 and Tyr168 of the AChBP subunit forming the complementary
Bgtx-binding site (in white) were rotated to prevent clashes
with Bgtx. Neither residue participates in secondary structure
elements.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
12406-12417)
copyright 2002.
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