Researchers from the Universities of Edinburgh, Goettingen, Tuebingen, and Strasbourg have discovered how a natural antibiotic called dermcidin, produced by the skin when humans sweat, is a highly efficient germ-fighting tool. The scientists uncovered the atomic structure of the compound and were then able to determine what makes dermcidin such an efficient weapon against dangerous germs.
When the skin is injured by a cut, scratch, or insect sting, antibiotic agents secreted in sweat glands kill the germs. These natural substances, called antimicrobial peptides, are more effective than man-made antibiotics as germs are not able to quickly develop resistance against them. They attack the weak point in the germs, their cell walls, which cannot be changed quickly to resist the attack. Scientists already knew that dermcidin was activated in salty, slightly acidic sweat. This sweat then forms tiny channels perforating germs’ cell membranes, which are stabilized by charged zinc particles in sweat. The water and charged particles flow uncontrollably across the membrane, killing harmful bugs.
The researchers used a combination of techniques to discover the atomic structure of the molecular channel and found it to be unusually long, permeable, and adaptable, representing a new class of membrane protein. The team found that dermcidin can adapt to widely variable types of membrane. They believe this explains why dermcidin is such an efficient broad-spectrum antibiotic and can fight off bacteria and fungi simultaneously. Dermcidin is active against many well-known organisms such as Mycobacterium tuberculosis and Staphylococcus aureus. The researchers hope that this finding can contribute to developing a new class of antibiotics that can kill some of these dangerous germs.
The full report, “Crystal Structure and Functional Mechanism of a Human Antimicrobial Membrane Channel,” is published online ahead of print in the journal Proceedings of the National Academy of Sciences of the United States of America (February 20, 2013; doi:10.1073/pnas.1214739110).