InterPro domain: IPR035144

The 20S proteasome, multisubunit proteolytic complex, is the central enzyme of nonlysosomal protein degradation in both the cytosol and nucleus. It is composed of 28 subunits arranged as four homoheptameric rings that stack on top of one another forming an elongated alpha-beta-beta-alpha cylinder with a central cavity. The proteasome alpha and beta subunits are members of the N-terminal nucleophile (Ntn)-hydrolase superfamily. Their N-terminal threonine residues are exposed as a nucleophile in peptide bond hydrolysis [ 1 ]. Mammals have 7 alpha and 7 beta proteasome subunits while archaea have one of each.

This entry represents the constitutive proteasome subunit alpha 1 [ 2 ], also known as Prosalpha6 (in Drosophila melanogaster ) [ 3 ] and Pre5 or alpha 6 (in fungi) [ 4 , 5 ]. This subunit is replaced in the D. melanogaster spermatoproteasome [ 6 ].

1. The proteasome. Annu Rev Biophys Biomol Struct 28, 295-317
2. The mouse Psma1 gene coding for the alpha-type C2 proteasome subunit: structural and functional analysis, mapping, and colocalization with Pde3b on mouse chromosome 7. Genomics 66, 313-23
3. The testis-specific proteasome subunit Prosalpha6T of D. melanogaster is required for individualization and nuclear maturation during spermatogenesis. Development 134, 3517-25
4. PRE5 and PRE6, the last missing genes encoding 20S proteasome subunits from yeast? Indication for a set of 14 different subunits in the eukaryotic proteasome core. Biochemistry 33, 12229-37
5. Structure of 20S proteasome from yeast at 2.4 A resolution. Nature 386, 463-71