Magainin

Magainin are a class of antimicrobial peptides found in the African clawed frog Xenopus laevis. They were discovered by Dr. Michael Zasloff and first reported in 1987.

Discovery

Zasloff was using the oocytes of Xenopus to study the nuclear transport and processing of tRNA. After removal of the ovaries of these frogs, Dr. Zasloff would suture the abdominal wounds and return the frogs to the aquarium he maintained in his laboratory. One day, many years into this research, he was struck by the remarkable manner in which these frogs healed. Wounds closed in the non-sterile tanks without any evidence of infection or visible inflammation. This "eureka" moment, his appreciating this "mysterious" process of healing, suggested to him that some mechanism had to exist by which these frogs fought off the microbes within the tank. He hypothesized that some form of antimicrobial agent was being expressed on the skin. Within several months these agents were isolated, chemically identified as peptides, and synthesized in the laboratory.

Their discovery represented the first example of an antimicrobial peptide produced in the skin of an animal, and complemented prior studies by Hans Boman of Sweden in the Cecropia moth, and Robert Lehrer (US) in rabbit white blood cells (defensins), supporting the widespread existence of antimicrobial peptides throughout nature. Thousands of antimicrobial peptides, similar to magainin, have been found throughout the plant and animal kingdoms. Many exhibit broad-spectrum antimicrobial activity, and can inhibit growth of numerous species of bacteria and fungi, as well as induce osmotic lysis of protozoa. These antimicrobial peptides are components of the "innate immune system" of animals and provide an important first line of antimicrobial defense.

An excellent review of antimicrobial peptides, covering their diversity and mechanism of action, has been published