The proteasome is a multicatalytic proteinase complex with a highly ordered ring-shaped 20S core structure. The core structure is composed of 4 rings of 28 non-identical subunits;2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. Proteasomes are distributed throughout eukaryotic cells at a high concentration and cleave peptides in an ATP/ubiquitin-dependent process in a non-lysosomal pathway. An essential function of a modified proteasome， the immunoproteasome， is the processing of class I MHC peptides. This gene encodes a member of the proteasome B-type family， also known as the T1B family， that is a 20S core beta subunit. Proteolytic processing is required to generate a mature subunit. Expression of this gene is induced by gamma interferon， and this gene product replaces catalytic subunit 2 (proteasome beta 7 subunit) in the immunoproteasome.