PDBsum entry 1txb

Neurotoxin

PDB id: 1txb

Contents

Protein chain

73 a.a.

References listed in PDB file

Key reference

Title

Solution structure of toxin b, A long neurotoxin from the venom of the king cobra (ophiophagus hannah).

Authors

S.S.Peng, T.K.Kumar, G.Jayaraman, C.C.Chang, C.Yu.

Ref.

J Biol Chem, 1997, 272, 7817-7823. [DOI no: 10.1074/jbc.272.12.7817]

PubMed id

9065446

Abstract

The solution structure of toxin b, a long neurotoxin (73 amino acids and 5 disulfides) from the venom of Ophiophagus hannah (king cobra), has been determined using 1H NMR and dynamical simulated annealing techniques. The structures were calculated using 485 distance constraints and 52 dihedral angle restraints. The 21 structures that were obtained satisfy the experimental restraints and possess good nonbonded contacts. Analysis of the converged structures revealed that the protein consists of a core region from which three finger-like loops extend outwards. The regular secondary structure in toxin b includes a double and a triple stranded antiparallel beta sheet. Comparison with the solution structures of other long neurotoxins reveals that although the structure of toxin b is similar to those of previously reported long neurotoxins, clear local structural differences are observed in regions proposed to be involved in binding to the acetylcholine receptor. A positively charged cluster is found in the C-terminal tail, in Loop III, and in the tip of Loop II. This cationic cluster could be crucial for the binding of the long neurotoxins to the acetylcholine receptor.

Figure 4.
Fig. 4. Sequence distribution of the NOE constraints used in the calculation of solution structures of Oh-8. The various NOE^ constraints used in the structure calculation include intra-residual (hatched), sequential (white), medium range (dotted), and long range (black).

Figure 9.
Fig. 9. GRASP representation of the distribution of the positively (blue) and negatively (red) charged residues of toxin b. The positively charged cluster constituted from cationic residues in the C-terminal tail, Loop III, and Loop II is involved in the^ binding of the toxin to the acetylcholine receptor.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (1997, 272, 7817-7823) copyright 1997.