Ubiquitin-binding protein that specifically recognizes and binds 'Lys-63'-linked ubiquitin. Does not bind 'Lys-48'-linked ubiquitin. Positively regulates the internalization of ligand-activated EGFR by binding to the Ub moiety of ubiquitinated EGFR at the cell membrane (By similarity). Interacts with EGFR (ubiquitinated); the interaction is direct and may regulate EGFR internalization. Interaction with EGFR may enhance association with the cell membrane.