Tripartite Tc toxin complexes of bacterial pathogens perforate the host membrane and translocate toxic enzymes into the host cell. These structures undergo a transition between a prepore to a pore state [1] and they are mainly constituted by closed beta-layer repeats. This Pfam entry includes a single repeat unit.

1: Mechanism of Tc toxin action revealed in molecular detail. Meusch D, Gatsogiannis C, Efremov RG, Lang AE, Hofnagel O, Vetter IR, Aktories K, Raunser S; Nature. 2014;508:61-65. PMID:24572368