Pore-forming exotoxin A (chain A; ExlA)  (Rasper and Merrill 1994; Méré et al., 2005).  Pore-formation has been demonstrated (Zalman and Wisnieski 1985).  Secretion depends on ExlB, a Two Partner Secretion (TPS; TC# 1.B.20) system, as well as type IV pili.  The protein has three domains: an N-terminal hemolyin domain, a central RGD motif domain, and a C-terminal domain required for cell lysis.  Pore-formation precedes lysis (Basso et al. 2017). ExlA triggers cadherin cleavage by promoting calcium influx which activates ADAM10 for proteolysis (Reboud et al. 2017).  ExlA possesses pore-forming activity and is cytolytic for most human cell types. It belongs to a class of poorly characterized bacterial toxins, sharing a similar protein domain organization and a common secretion pathway (Huber 2022).