Archeal proteasome, beta subunit. The 20S proteasome, multisubunit proteolytic complex, is the central enzyme for non-lysosomal protein degradation in both the cytosol and the 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 both members of the N-terminal nucleophile (Ntn)-hydrolase superfamily. Their N-terminal threonine residues are exposed as a nucleophile in peptide bond hydrolysis. Mammals have 7 alpha and 7 beta proteasome subunits while archaea have one of each.
Jiyao W et al.(2023). "The conserved domain database in 2023.",