BOTULINUM NEUROTOXIN TYPE-E - STUDIES ON MECHANISM OF ACTION AND ON STRUCTURE-ACTIVITY-RELATIONSHIPS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 224  (1) , 135-140
Abstract
Single chain type E botulinum neurotoxin was isolated from culture fluids of Clostridium botulinum (strain Alaska E-43). The neurotoxin, which migrated as a single band in polyacrylamide gel electrophoresis with sodium dodecyl sulfate, had a MW of .apprx. 147,000. Single chain type E neurotoxin that was exposed to trypsin was converted to a dichain molecule. Pretreatment of the single chain molecule with 1,2-cyclohexanedione, a reagent that selectively modifies arginine residues, inhibited trypsin-induced generation of the dichain molecule. In dose-response experiments (10-13-10-9 M) on the isolated neuromuscular junction (phrenic nerve-hemidiaphragm preparation), the dichain neurotoxin was .apprx. 2 orders of magnitude more potent than the single chain neurotoxin. Neither species of neurotoxin (1 pmol/mouse, in vivo; 1 .times. 10-11 M, in vitro) was very effective in blocking autonomic transmission (vagus nerve-atrium preparation). The neuromuscular blocking action of the dichain molecule was divided into a sequence of 3 steps. There was an initial binding step that was relatively rapid, little influenced by temperature and which left the neurotoxin partially accessible to the neutralizing effects of antitoxin. There was a translocation step that was temperature-dependent, antagonized by ammonium chloride and methylamine hydrochloride, and caused the neurotoxin to become inaccessible to the neutralizing effects of antitoxin. There was an intracellular lytic step, during which the toxin blocked excitation-secretion coupling.

This publication has 0 references indexed in Scilit: