Scientists map complete structure of deadly botulinum toxin complex for first time

Stephanie Baum
scientific editor

Robert Egan
associate editor

Researchers at Stockholm University have succeeded in creating a molecular blueprint of how one of the world's most dangerous toxins, botulinum toxin, is structured, stabilized, delivered and released. The research, published in Science Advances, paves the way for more effective drugs.
Botulinum toxin is the strongest poison known to man—a million times more toxic than that found in cobra venom. The toxin is produced by the bacterium Clostridium botulinum. The toxin causes the serious illness botulism. However, the toxin also has many medical uses, for treating chronic migraine, muscle spasms and severe sweating, as well as for cosmetic purposes.
"In nature, the toxin does not act alone. It travels within a large, 14-part protein complex, which shields the toxin from the harsh environment in the gut and helps it cross from the gut into the blood, where the toxin is released to circulate until it finds its ultimate target, the connection between the nerves and the muscle," says PÃ¥l Stenmark, research director and professor of neurochemistry at Stockholm University.
For the first time, researchers have now succeeded in visualizing the entire large toxin complex.
"We have studied the toxin complex found in the drug NeuroBloc, which is closely related to Botox," they report.
To map the large toxin complex, scientists used cryo-electron microscopy.
"It is a Nobel Prize-winning imaging technique where we flash-freeze molecules and capture thousands of snapshots of the molecules, which we then combine into a 3D picture at near-atomic resolution," says Stenmark.
The molecular blueprint opens up new possibilities.
"It offers new opportunities to neutralize the toxin or harness its mechanisms for therapeutic use. But above all, it is very exciting to gain insight into how this complex system works and what it looks like," says Stenmark.
More information: Structure of the Complete 14-subunit Botulinum Neurotoxin B Complex Reveals a Unique Anchoring Through the Narrow Central Pore of HA70, Science Advances (2025).
Journal information: Science Advances
Provided by Stockholm University