PDBsum entry 1f94

Toxin

PDB id: 1f94

Contents

Protein chain

63 a.a.

Waters ×118

PDB id:

1f94

Name:

Toxin

Title:

The 0.97 resolution structure of bucandin, a novel toxin isolated from the malayan krait

Structure:

Bucandin. Chain: a

Source:

Bungarus candidus. Organism_taxid: 92438. Secretion: venom

Resolution:

0.97Å R-factor: 0.123 R-free: 0.177

Authors:

P.Kuhn,A.M.Deacon,S.Comoso,G.Rajaseger,R.M.Kini,I.Uson,P.R.Kolatkar

Key ref:

P.Kuhn et al. (2000). The atomic resolution structure of bucandin, a novel toxin isolated from the Malayan krait, determined by direct methods. Acta Crystallogr D Biol Crystallogr, 56, 1401-1407. PubMed id: 11053837 DOI: 10.1107/S0907444900011501

Date:

06-Jul-00 Release date: 26-Jul-00

Protein chain

P81782  (3NOJ_BUNCA) -  Bucandin from Bungarus candidus

Seq: 63 a.a.

Struc: 63 a.a.

DOI no: 10.1107/S0907444900011501

Acta Crystallogr D Biol Crystallogr 56:1401-1407 (2000)

PubMed id: 11053837

The atomic resolution structure of bucandin, a novel toxin isolated from the Malayan krait, determined by direct methods.

P.Kuhn, A.M.Deacon, S.Comoso, G.Rajaseger, R.M.Kini, I.Usón, P.R.Kolatkar.

ABSTRACT

Bucandin is a novel presynaptic neurotoxin isolated from Bungarus candidus (Malayan krait). It has the unique property of enhancing presynaptic acetylcholine release and represents a family of three-finger toxins with an additional disulfide in the first loop. There are no existing structures from this sub-category of three-finger toxins. The X-ray crystal structure of bucandin has been determined by the Shake-and-Bake direct-methods procedure. The resulting electron-density maps were of outstanding quality and allowed the automated tracing of 61 of the 63 amino-acid residues, including their side chains, and the placement of 48 solvent molecules. The 0.97 A resolution full-matrix least-squares refinement converged to a crystallographic R factor of 12.4% and the final model contains 118 solvent molecules. This is the highest resolution structure of any member of the three-finger toxin family and thus it can serve as the best model for other members of the family. Furthermore, the structure of this novel toxin will help in understanding its unique ability to enhance acetylcholine release. The unique structure resulting from the fifth disulfide bond residing in the first loop improves the understanding of other toxins with a similar arrangement of disulfide bonds.

Selected figure(s)

Figure 2.
Figure 2 Electron-density maps obtained from (a) SnB v2.0, (b) the final refined model (2F[o] - F[c]). The maps are contoured at 1.0 (gray) and 5.0 (magenta).

Figure 5.
Figure 5 Structural comparisons of (a) bucandin with cobratoxin (1ctx), (b) erabutoxin (3ebx) and (c) bungarotoxin (2abx). Bucandin is colored orange in each figure. The similarity of structures is apparent, as well as the significant differences within the loop regions. The nearly 90° turn of the first loop of bucandin relative to the rest of the molecule shows a significant difference compared with other toxins. The presence of a fourth -strand in bucandin is clearly seen on the left of the molecule.

The above figures are reprinted by permission from the IUCr: Acta Crystallogr D Biol Crystallogr (2000, 56, 1401-1407) copyright 2000.

Figures were selected by an automated process.