Polysaccharide-binding protein probably involved in ulvan degradation (Probable). Ulvan is the main polysaccharide component of the Ulvales (green seaweed) cell wall. It is composed of disaccharide building blocks comprising 3-sulfated rhamnose (Rha3S) linked to D-glucuronic acid (GlcA), L-iduronic acid (IduA), or D-xylose (Xyl) (Probable). The SusD-like protein may mediate ulvan oligomer-binding before transport in the periplasm for further degradation (By similarity). By ulvan and rhamnose. Belongs to the SusD family.