Acts as a scaffolding protein in the cellulosome. It promotes binding of cellulose to the catalytic domains of the cellulolytic enzymes probably through the binding of the nine repeated domains with dockerin domains present in catalytic subunits of the cellulosome. Remains at cell surface. The cohesin domains bind to the dockerin domain born by the catalytic components of the cellulosome. O-glycosylated on most but not all Thr residues of the linker units.