Crystallization and preliminary X-ray analysis of candoxin, a novel reversible neurotoxin from the Malayan krait Bungarus candidus

Palasingam Paaventhan, Jeremiah S. Joseph, Selvanayagam Nirthanan, Ganapathy Rajaseger, Ponnampalam Gopalakrishnakone, Manjunatha R. Kini, Prasanna Kolatkar

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2 Citations (Scopus)

Abstract

Candoxin, a novel three-finger toxin from Bungarus candidus, is a reversible antagonist of muscle (αβγδ) but a poorly reversible antagonist of neuronal α7 nicotinic acetylcholine receptors. It has a molecular weight of 7344 Da, with 66 amino-acid residues including ten half-cystines. The fifth disulfide bridge is located at the tip of loop I (Cys6-Cys11) instead of in loop II as found in other α-neurotoxins. Interestingly, candoxin lacks the segment cyclized by the fifth disulfide bridge at the tip of the middle loop of long-chain neurotoxins, which was reported to be critical for binding to α7 receptors. As a first step to determining its three-dimensional structure, candoxin was crystallized by the hanging-drop vapour-diffusion technique in conditions around 1.5 M sodium chloride, 10%(v/v) ethanol. The crystals formed belonged to the hexagonal system, space group P6222, with unit-cell parameters a = 54.88, b = 54.88, c = 75.54 Å, α = β = 90, γ = 120°, and diffract to a resolution of 1.80 Å. The crystallographic asymmetric unit contains one molecule of candoxin, with an estimated solvent content of 44.6%. Attempts to solve these structures by molecular-replacement methods have not been successful and a heavy-atom derivative search has been initiated.

Original languageEnglish
Pages (from-to)584-586
Number of pages3
JournalActa Crystallographica - Section D Biological Crystallography
Volume59
Issue number3
DOIs
Publication statusPublished - 1 Mar 2003
Externally publishedYes

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ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Biophysics
  • Condensed Matter Physics
  • Structural Biology

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