PA28alpha (human) (rec.) (untagged)

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 immuno-proteasome, is the processing of class I MHC peptides. The immuno-proteasome contains an alternate regulator, referred to as the 11S regulator or PA28 that replaces the 19S regulator. PA28 alpha is implicated in immunoproteasome assembly and required for efficient antigen processing. The PA28 activator complex enhances the generation of class I binding peptides by altering the cleavage pattern of the proteasome. The PA28 complex is expressed constitutively in antigen-presenting cells, its expression is up-regulated by interferongamma, and it appears to be involved in the presentation of endogenous antigens by MHC class I molecules. The PA28 alpha protein was recombinantly expressed in E. coli.