Recombinant human PA28gamma/PSME3 protein was determined by SDS-PAGE with Coomassie Blue.
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.
