The proteasome is a multicatalytic proteinase complex which holds an extremely organized 20S core structure shaped like a ring. The central structure is assembled from 4 rings of 28 non-identical subunits； 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits. There is a high concentration of proteasomes all over the eukaryotic cells and their job is to cleave peptides in an ATP/ubiquitin-dependent procedure in a non-lysosomal pathway. PSMA3 encodes several of the peptidase T1A family which is a 20S core alpha subunit. Two alternative transcripts encoding diverse isoforms were recognized.
