Localization of sites for 125I-labelled botulinum neurotoxin at murine neuromuscular junction and its binding to rat brain synaptosomes

J. O. Dolly, R. S. Williams, J. D. Black, C. K. Tse, P. Hambleton, J. Melling

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Botulinum neurotoxin, purified to homogeneity from Clostridium botulinum (Type A), was found to be highly neurotoxic (>8 x 107 mouse ld50/mg protein). Labelling of this pure neurotoxin with 125I-iodine to high specific radioactivity was achieved without appreciable loss of biological activity. This was used to demonstrate saturable binding sites for this toxin at the neuromuscular junction, following in vivo administration into mice. A demonstrable inhibitory effect of the neurotoxin on release of acetylcholine from rat cerebrocortical synaptosomes indicates that it affects synapses in the central nervous system. Kinetic studies on the binding of 125I-labelled neurotoxin to brain synaptosomes yielded an association rate constant of 2.3 x 105M-1s-1; dissociation plots were biphasic and the predominant species showed a rate constant of 1.2 x 10-4s-1. The saturable binding component is heatsensitive and inactivated by trypsin. Preliminary studies showed that botulinum neurotoxin associates with plasma membrane fractions of synaptosomes and that binding does not result in any gross structural changes, at least in the majority of the toxin molecules.

Original languageEnglish (US)
Pages (from-to)141-148
Number of pages8
Issue number1
StatePublished - 1982
Externally publishedYes


  • Botulinum neurotoxin
  • I-iodination
  • acetylcholine release
  • autoradiography
  • binding sites
  • kinetics
  • localization
  • synaptosomes

ASJC Scopus subject areas

  • Toxicology


Dive into the research topics of 'Localization of sites for <sup>125</sup>I-labelled botulinum neurotoxin at murine neuromuscular junction and its binding to rat brain synaptosomes'. Together they form a unique fingerprint.

Cite this