Inhibits the classical pathway of complement activation and prevents accumulation of deposited C4. 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. Finally, the mature protein remains tightly associated with the bacterium. A 31- to 39-amino-acid region found immediately upstream of the translocator domain is essential for surface expression.