1KC4: NMR Structural Analysis of the Complex Formed Between alpha-Bungarotoxin and the Principal alpha-Neurotoxin Binding Sequence on the alpha7 Subunit of a Neuronal Nicotinic Acetylcholine Receptor

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.
PDB ID: 1KC4Download
MMDB ID: 18943
PDB Deposition Date: 2001/11/7
Updated in MMDB: 2007/11
Experimental Method:
solution nmr
Source Organism:
Bungarus multicinctus
Similar Structures:
Molecular Components in 1KC4
Label Count Molecule
Proteins (2 molecules)
Molecule annotation
Neuronal Acetylcholine Receptor Protein, Alpha-7 Chain(Gene symbol: CHRNA7)
Molecule annotation
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Citing MMDB