How proteins disable bacterial toxins

New research shows that small proteins called defensins, which are active in the immune system, neutralise toxins released by bacteria.

These proteins, the first line of defence when a pathogen invades the body can disable bacterial toxins by exploiting a property that makes the toxins - which are also proteins - effective but also turns out to be their weakness.

This makes defensins a potentially promising model for the development of drugs that could mimic their activity and reduce a pathogens' infectious power.

"An important part of our findings is that defensin offer universal protection. Not every single toxin will be affected but many toxins will," said Dmitri Kudryashov, assistant professor of chemistry and biochemistry at the Ohio State University in the US.

These toxins, which are released by bacteria, have malleable surfaces that allow them to move through porous areas of host cells to pave the way for bacteria to stay alive.

But that same malleability makes the toxins vulnerable to these immune system proteins which bind to the toxins and render them useless.

In a previous paper, Kudryashov and colleagues described how the toxins' lack of structural rigidity is a secret to their success - they can unfold themselves to cross a host cell membrane and then refold into their toxic structure on the other side, within the cell.

Defensins can exploit the toxins' ability to change their structure by attaching to specific locations on these proteins, triggering misfolding to occur at an inopportune time.

"Defensins become part of the toxin that is not properly folded. They integrate into the toxin in such a way that means it basically cannot accomplish its functions," Kudryashov added.

The research team is now testing defensins' effectiveness against viral proteins.

The research appeared in the journal Immunity.