Component of the 26S proteasome, a multiprotein complex involved in the ATP-dependent degradation of ubiquitinated proteins. This complex plays a key role in the maintenance of protein homeostasis by removing misfolded or damaged proteins, which could impair cellular functions, and by removing proteins whose functions are no longer required (PubMed:21098295). Therefore, the proteasome participates in numerous cellular processes, including cell cycle progression, apoptosis, or DNA damage repair. Within the complex, functions as a proteasomal ubiquitin receptor (Probable). Component of the 19S proteasome regulatory particle complex (PubMed:21098295). The 2 S.pombe rpn13 homologs, rpn1301 and rpn1302 are present at a 0.2-1 ratio (PubMed:21098295). The Pru (pleckstrin-like receptor for ubiquitin) domain mediates interactions with rpn2 and ubiquitin. Belongs to the ADRM1 family. The c-terminal sequence diverges from classical ADRM1 family proteins.