<p>This entry represents a structural domain consisting of a beta-sandwich fold with an immunoglobulin-like Greek-key topology, and a beta-ribbon arm that forms an oligomeric transmembrane barrel. This domain is found in pore-forming proteins, including porin MspA, as well as the exotoxins haemolysin and leukocidin. MspA is a membrane porin produced by Mycobacteria, allowing hydrophilic nutrients to enter the bacterium [<cite idref="PUB00031908"/>]. Haemolysins attack blood cell membranes and cause cell rupture by forming water-filled homoheptameric transmembrane pores. Leukocidin consists of two polypeptides, F and S, and form pores in polymorphonuclear leukocytes [<cite idref="PUB00042629"/>]. </p> Leukocidin/porin