Structural domains comprising this superfamily share the structure of a large family of uncharacterised proteins which are mostly found in human gut bacteroides, but also some environmental and water bacteria (Planctomycetes) and metagenomic samples. Most of these are either secreted proteins or located on the outer surface. The solved structure of a Bacteroides ovatus homologue, which adopts a galactose binding (jelly-roll) beta barrel structure, suggests that they are involved in cell-cell interactions or cell-nutrient interactions.