Defensins are a class of small proteins that play a critical role in the innate immune system of various organisms, including humans and other animals. These peptides are known for their broad-spectrum antimicrobial activity and are produced by various cells, particularly those of epithelial tissues.
Structurally, defensins consist of a relatively short chain of amino acids, typically comprising about 29-58 residues, and are characterized by specific structural motifs known as beta-sheets and alpha-helices. These motifs contribute to the three-dimensional structure of defensins which enables their antimicrobial activity.
One of the primary functions of defensins is to protect organisms from microbial infections by disrupting the integrity of microbial cell membranes. They are highly effective against a wide range of microorganisms including bacteria, fungi, and certain viruses. Defensins work by forming pores in the lipid bilayer of the microbial cell membrane, leading to leakage of cellular contents and ultimately microbial death.
In addition to their direct antimicrobial action, defensins also possess immunomodulatory properties. They can attract and activate immune cells, such as neutrophils and macrophages, promoting an efficient immune response against invading pathogens.
Defensins are found in various tissues, including the respiratory and gastrointestinal tracts, skin, and reproductive organs. They are synthesized and secreted by specialized cells like Paneth cells in the intestine, neutrophils, and epithelial cells of various organs. Deficiencies or abnormalities in defensin production have been associated with increased susceptibility to infections.
Overall, defensins are essential components of the innate immune system, playing a crucial role in protecting organisms from microbial invasion and maintaining homeostasis in various tissues.
