Proteasome subunit beta type-7（PSMB7) belongs to the proteasome B-type family. PSMB7 is a multicatalytic proteinase complex with an extremely ordered ring-shaped 20S core structure. This core structure is comprised of 4 rings of 28 non-identical subunits； 2 rings are comprised of 7 alpha subunits and 2 rings are comprised of 7 beta subunits. Proteasomes are scattered all over eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent manner in a non-lysosomal pathway. The processing of class I MHC peptides is a vital function of the immunoproteasome（which is a modified proteasome).
