Essential fimbrial adhesion factor that mediates binding to N-acetylglucosamine-containing receptors in the host intestinal microvilli, leading to colonization of the intestinal tissue, and diarrhea or septicemia. Also confers adhesiveness to laminin and basement membranes. May be involved in the initiation of polymerization of fimbrillin monomers during fimbrial filament biogenesis. Attached to the tip of the fimbrial filaments. Belongs to the fimbrial protein family.