Protein in tears use ‘ jaws’ to chew through bacteria

Human tears are thought to be unique in the animal kingdom, in that they’re often tied to our emotional state — but that’s not the only special property they possess. Proteins in tears can protect against harmful bacteria, and now a team of University of California- Irvine researchers has shown how.

Lysozymes are antiseptic proteins found in a number of bodily fluids, including tears. Their anti- bacterial properties were first identified by Nobel laureate Alexander Fleming, discoverer of penicillin, in the 1920s, but it was unclear how these proteins could take out bacteria much bigger than them. The body’s defensive army of white blood cells, after all, protects by engulfing and destroying invading bacteria; lysozymes must work by a very different mechanism.

Now, in a paper released online by the journal Science, researchers have found that these proteins work by using “jaws” to chew through cell walls, destroying the bacteria in the process.

Figuring this out was no easy task: As the protein binds with the molecule it’s affecting, it undergoes subtle shape changes that can tell researchers what exactly the protein is doing. The problem is, this process is hard to keep track of. The scientists had to build a tiny transistor and stuck a single protein molecule on its carbonnanotube live wire, essentially tracking the electronic “noise” the protein gave off as it shifted around.

The technique they used will, they hope, also be useful in detecting cancerous molecules, long before conventional detection methods would pick up signs of the disease.