Acanthaporin is a pore-forming toxin from acanthamoebae, an opportunistic pathogen. This protein is cytotoxic for neuronal cells in humans and shows antimicrobial activity against diverse bacterial strains by permeabilising their membranes. It folds into a disulfide-bonded four-alpha-helix monomeric structure that dimerises at pH 8.0 due to the deprotonation of some histidine residues, which leads to a conformational change [1].

1: Structure and function of a unique pore-forming protein from a pathogenic acanthamoeba. Michalek M, Sonnichsen FD, Wechselberger R, Dingley AJ, Hung CW, Kopp A, Wienk H, Simanski M, Herbst R, Lorenzen I, Marciano-Cabral F, Gelhaus C, Gutsmann T, Tholey A, Grotzinger J, Leippe M; Nat Chem Biol. 2013;9:37-42. PMID:23143413