Major protein secreted in laboratory media showing proteolytic activity. May be involved in invasion and destruction of host intestinal epithelium. Inhibited by the serine protease inhibitor PMSF, but not by benzamidine, alpha 1-antitrypsin, alpha 1-antichymotrypsin. Not inhibited by metalloprotease inhibitors such as EDTA and orthophenanthroline. Optimum temperature is 37 degrees Celsius. 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. Cleavage is performed by an unknown protease. Mutants exhibit an attenuated virulence in the rabbit ligated ileal loop model.