4RUD

Crystal structure of a three finger toxin


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.95 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.204 

Starting Model: experimental
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wwPDB Validation   3D Report Full Report


This is version 1.5 of the entry. See complete history


Literature

Fulditoxin, representing a new class of dimeric snake toxins, defines novel pharmacology at nicotinic ACh receptors.

Foo, C.S.Jobichen, C.Hassan-Puttaswamy, V.Dekan, Z.Tae, H.S.Bertrand, D.Adams, D.J.Alewood, P.F.Sivaraman, J.Nirthanan, S.Kini, R.M.

(2020) Br J Pharmacol 177: 1822-1840

  • DOI: https://doi.org/10.1111/bph.14954
  • Primary Citation of Related Structures:  
    4RUD

  • PubMed Abstract: 

    Animal toxins have contributed significantly to our understanding of the neurobiology of receptors and ion channels. We studied the venom of the coral snake Micrurus fulvius fulvius and identified and characterized the structure and pharmacology of a new homodimeric neurotoxin, fulditoxin, that exhibited novel pharmacology at nicotinic ACh receptors (nAChRs). Fulditoxin was isolated by chromatography, chemically synthesized, its structure determined by X-ray crystallography, and its pharmacological actions on nAChRs characterized by organ bath assays and two-electrode voltage clamp electrophysiology. Fulditoxin's distinct 1.95-Å quaternary structure revealed two short-chain three-finger α-neurotoxins (α-3FNTxs) non-covalently bound by hydrophobic interactions and an ability to bind metal and form tetrameric complexes, not reported previously for three-finger proteins. Although fulditoxin lacked all conserved amino acids canonically important for inhibiting nAChRs, it produced postsynaptic neuromuscular blockade of chick muscle at nanomolar concentrations, comparable to the prototypical α-bungarotoxin. This neuromuscular blockade was completely reversible, which is unusual for snake α-3FNTxs. Fulditoxin, therefore, interacts with nAChRs by utilizing a different pharmacophore. Unlike short-chain α-3FNTxs that bind only to muscle nAChRs, fulditoxin utilizes dimerization to expand its pharmacological targets to include human neuronal α4β2, α7, and α3β2 nAChRs which it blocked with IC 50 values of 1.8, 7, and 12 μM respectively. Based on its distinct quaternary structure and unusual pharmacology, we named this new class of dimeric Micrurus neurotoxins represented by fulditoxin as Σ-neurotoxins, which offers greater insight into understanding the interactions between nAChRs and peptide antagonists.


  • Organizational Affiliation

    Protein Science Laboratory, Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore.


Macromolecules
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Three-finger toxin 3b
A, B
58Micrurus fulviusMutation(s): 0 
UniProt
Find proteins for U3EPL2 (Micrurus fulvius)
Explore U3EPL2 
Go to UniProtKB:  U3EPL2
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupU3EPL2
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.95 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.201 
  • R-Value Observed: 0.204 
  • Space Group: P 4 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 58.8α = 90
b = 58.8β = 90
c = 70.567γ = 90
Software Package:
Software NamePurpose
ADSCdata collection
PHASERphasing
PHENIXrefinement
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2016-05-18
    Type: Initial release
  • Version 1.1: 2017-11-22
    Changes: Refinement description
  • Version 1.2: 2018-07-18
    Changes: Data collection, Database references
  • Version 1.3: 2020-01-22
    Changes: Database references, Source and taxonomy, Structure summary
  • Version 1.4: 2022-08-24
    Changes: Database references, Derived calculations
  • Version 1.5: 2023-11-08
    Changes: Data collection, Refinement description