Involved in intestinal colonization, displays in vitro mucinolytic activity, serum resistance, and hemagglutination. Important to penetrate the intestinal mucus layer. The cleaved C-terminal fragment (autotransporter domain) is localized in the outer membrane. The signal peptide, cleaved at the inner membrane, guides the autotransporter protein to the periplasmic space. Then, insertion of the C-terminal translocator domain in the outer membrane forms a hydrophilic pore for the translocation of the passenger domain to the bacterial cell surface, with subsequent cleavage (By similarity). Cleaved to release the mature protein from the outer membrane. The S.flexneri genes encoding ShET1 enterotoxin subunits set1A and set1B are contained within the pic gene, on the complementary non-coding strand.