Molecular Blueprint Reveals Structure and Delivery of Botulinum Toxin

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 the scientific journal 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."

Pål Stenmark, research director and professor of neurochemistry, Stockholm University

For the first time, researchers have now succeeded in visualising the entire large toxin complex.

"We have studied the toxin complex found in the drug NeuroBloc, which is closely related to Botox."

To map the large toxin complex, scientists used cryo-electron microscopy.

"It is a Nobel Prize winning imaging technique were we flash-freeze molecules and captures thousands of snapshots of the molecules, which we then combined into a 3D picture at near-atomic resolution," says Pål 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 Pål Stenmark.