Probably interacts with GlcNAc residues. May promote attachment to both epithelial cell surfaces and chitin. This function enhances bacterial colonization in the gastrointestinal tract and may also be important in the environment by augment colonization of chitinous structures, leading to improved survival. Promotes bacterial attachment to, and colonization of, zooplankton in the aquatic ecosystem. Secreted via the type II secretion pathway EPS (extracellular protein secretion). Belongs to the GbpA family.