Defensins comprise a structural class of small cationic peptides that exert broad-spectrum antimicrobial activities through membrane permeabilization. Their predominantly beta-sheet structure, stabilized by three disulfide bonds, distinguishes them from other antimicrobial peptides which typically form amphiphilic helices. Defensins bind to membranes electrostatically and subsequently form apparently multimeric pores. Recent structural and biophysical studies are beginning to provide insights into the process of permeabilization.
