Collagen-binding outer membrane protein forming a fibrillar matrix on the bacterial cell surface and phagocytosis resistance (By similarity). Promotes initial attachment and invasion of eukaryotic cells (Probable). Also protects the bacteria by being responsible for agglutination, serum resistance and complement inactivation. Gly-389 plays an important role in this protein; replacing it with increasingly large polar residues decreases expression levels and trimer stability. Residues larger than Ser (Thr, Asn or His) significantly decrease serume resistance and bacterial autoagglution without affecting adhesion to host cells or host cell cytokine production (PubMed:17921300). Homotrimer; trimers are very stable, not disrupted by heating at 95 degrees Celsius for 10 minutes in SDS sample buffer. The C-terminal translocator domain is localized in the outer membrane and the passenger domain is at the cell surface. The signal peptide, cleaved at the inner membrane, guides the autotransporter protein to the periplasmic space. Then, insertion of the trimerized C-terminal translocator domain in the outer membrane forms a hydrophilic pore for the translocation of the passenger domain to the bacterial cell surface. The passenger domain is probably exported as a hairpin structure, with all 3 strands of the trimer in the pore simultaneously. Expression of mutant proteins in E.coli is improved in a degP deletion, suggesting the mutants are susceptible to degradation in the periplasm. Belongs to the autotransporter-2 (AT-2) (TC 1.B.40) family.