Members of this family are found in Pseudomonas aeruginosa exotoxin A, and are responsible for transmembrane targeting of the toxin, as well as transmembrane translocation of the catalytic domain into the cytoplasmic compartment. A furin cleavage site is present within the domain: cleavage generates a 37 kDa carboxy-terminal fragment, which includes the enzymatic domain, which is then is translocated into the cytoplasm. The domain adopts a helical structure, with six alpha-helices forming a bundle [1].

1: Refined crystallographic structure of Pseudomonas aeruginosa exotoxin A and its implications for the molecular mechanism of toxicity. Wedekind JE, Trame CB, Dorywalska M, Koehl P, Raschke TM, McKee M, FitzGerald D, Collier RJ, McKay DB; J Mol Biol. 2001;314:823-837. PMID:11734000