Involved in cell aggregation, biofilm formation, and adhesion to human intestinal epithelial cells. Homotrimer. The C-terminal translocator domain is localized in the outer membrane and the passenger domain is at the cell surface (By similarity). Proper surface expression requires SadB (PubMed:24369174). 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 (By similarity). The surface exposed region contains four YadA-like head domains and extended stalk regions, multiply segmented by FGG, HANS, DALL and neck motifs (PubMed:23213248). In vitro, loss of sadA does not affect cell aggregation, biofilm formation and adhesion to epithelial cells. Disruption does not affect the course of infection. Immunization of mice with folded, full-length, purified SadA elicits an IgG response which provides limited protection against bacterial challenge. Belongs to the autotransporter-2 (AT-2) (TC 1.B.40) family.