| Description : |
PA28 (also called the 11S regulatory complex) is another activator of the 20S proteasome, which assembles on either one or both ends of the 20S proteasome in an ATP-independent manner. PA28 can greatly enhance the peptidase activities of the 20S proteasome, but not for degradation of ubiquitinated proteins. The PA28 activator is a complex of two alternating homologous subunits, PA28α and PA28β, which assembles as a hexameric ring with an α3β3 stoichiometry. PA28α and PA28β are induced by interferon. Functionally, PA28 enhances the generation of class I peptides for antigen presentation. The third subunit, PA28γ, was recently identified in the nucleus. Recombinant PA28α and PA28β form a heptomeric ring; whereas PA28γ forms a hexameric ring. All of them can stimulate the peptidase activities of the 20S proteasome. |
