Defensins are small (30-35 residue) cysteine rich cationic proteins found in vertebrate phagocytes (notably the azurophil granules of neutrophils) and active against bacteria, fungi and enveloped viruses. Most defensins function via penetrating the microbial's cell membrane by way of electrical attraction, and once embedded, forming a pore in the membrane which allows efflux. A residue, broadly, is anything left behind by a reaction or event. ... Cysteine is a naturally occurring hydrophobic amino acid which has a sulfhydryl group and is found in most proteins, however only in small quantities. ... In chemistry, a cationic species is one that contains a full positive charge. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Groups Conodonta Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi (early jawless fish) Thelodonti Anaspida Cephalaspidomorphi (early jawless fish) Galeaspida Pituriaspida Osteostraci Gnathostomata (jawed vertebrates) Placodermi Chondrichthyes (cartilaginous fish) Acanthodii Osteichthyes (bony fish) Actinopterygii (ray-finned fish) Sarcopterygii (lobe-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Tetrapoda Amphibia Amniota Sauropsida/(Reptiles) Aves (Birds) Synapsida Mammalia... A phagocyte is a cell that ingests (and destroys) foreign matter, such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by cellular digestion. ... Azurophil is referred to the readily staining with an azure dye. ... An assortment of grains The word grain has a great many meanings, most being descriptive of a small piece or particle. ... Neutrophil granulocytes, generally referred to as neutrophils, are a class of white blood cells and are part of the immune system. ... Kingdoms/Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular: bacterium) are a major group of living organisms. ... Divisions Chytridiomycota Deuteromycota Zygomycota Glomeromycota Ascomycota Basidiomycota Fungus growing on a tree in Borneo A fungus (plural fungi) is a eukaryotic organism that digests its food externally and absorbs the nutrient molecules into its cells. ... A common alternate meaning of virus is computer virus. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... Drawing of a cell membrane A component of every biological cell, the selectively permeable cell membrane (or plasma membrane or plasmalemma) is a thin and structured bilayer of phospholipid and protein molecules that envelopes the cell. ...

The underlying genes responsible for defensin production are highly polymorphic. Some aspects are conserved, however; the hallmarks of a β-defensin are its small size, high density of cationic charge and six-cysteine-residue motif. Generally they are encoded by two-exon genes, where the first exon encodes for a hydrophobic leader sequence and the second for a peptide containing the cysteine motif. In general, polymorphism describes multiple possible states for a single property (it is said to be polymorphic). ...

There are three main (known) forms of defensins; α-defensins, β-defensins, and θ-defensins. α-defensins are expressed primarily in neutrophils as well as macrophages and the Paneth cells of the intestines (where they help maintain the correct microbial balance). β-defensins are the most widely distributed, being secreted by leukocytes and epithelial cells of many kinds. For example, they can be found on the tongue, skin, cornea, salivary glands, kidneys, oesophagus, and respiratory tract. It is theorised that one of the causes of cystic fibrosis is inhibition of β-defensin activity on the epithelial surfaces of the lungs and trachaea due to higher salt content. θ-defensins are rare, and thus far have been found only in the leukocytes of the rhesus macaque. Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... White Blood Cells is also the name of a White Stripes album. ... In zootomy, epithelium is a tissue composed of a layer of cells. ... Binomial name Macaca mulatta Zimmermann, 1780 The Rhesus Macaque (Macaca mulatta), often called the Rhesus Monkey, is one of the best known species of Old World monkeys. ...

In immature marsupials, due to the fact that their immune system is underdeveloped at the time of birth, defensins play a major role in defense against pathogens. They are produced in the milk of the mother as well as by the young marsupial in question. It is also interesting to note that retrocyclin- a defensin created artificially by `fixing' a human psuedogene- is effective against HIV, though the mechanism by which it does this is unknown. Orders Superorder Ameridelphia Didelphimorphia Paucituberculata Superorder Australidelphia Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Marsupials are mammals in which the female typically has a pouch (called the marsupium, from which the name Marsupial derives) in which it rears its young through early infancy. ... The immune system is the system of specialised cells and organs that protect an organism from outside biological influences. ... A pathogen (literally birth of pain from the Greek παθογένεια) is a biological agent that can cause disease to its host. ...