Ubiquitin-binding protein involved in the resistance to phenanthroline, sanguinarine, nordihydroguaiaretic acid (NDGA), isopropyl (N-3-chloro-phenyl)-carbamate (IPCPC) and guanosine 5'-O-(2-thiodiphosphate). Interacts (via its WD repeats) with ubiquitin. The N-terminal WD repeats are involved in ubiquitin-binding. Present with 589 molecules/cell in log phase SD medium.