InterPro domain: IPR016295

This group represents the beta type-4 subunit (MEROPS identifier T01.987) from the proteasome endopeptidase complex, which is one of the non-peptidase subunits. This subunit is known as beta type-7 in fungi.

The 20S proteasome, multisubunit proteolytic complex, is the central enzyme of non-lysosomal protein degradation in both the cytosol and nucleus [ 1 ]. 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 [ 2 , 3 ]. The proteasome alpha and beta subunits are members of the N-terminal nucleophile (Ntn)-hydrolase superfamily [ 4 ]. Three of the beta subunits (beta1, beta2 and beta5) have an N-terminal threonine residue exposed as a nucleophile in peptide bond hydrolysis [ 5 ]. Eukaryotes have 7 alpha and 7 beta proteasome subunits while archaea have one of each [ 6 ].

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3. The proteasome. Annu Rev Biophys Biomol Struct 28, 295-317
4. Structural comparison of Ntn-hydrolases. Protein Sci. 9, 2329-37
5. Identification of the yeast 20S proteasome catalytic centers and subunit interactions required for active-site formation. Proc. Natl. Acad. Sci. U.S.A. 94, 7156-61
6. A comprehensive view on proteasomal sequences: implications for the evolution of the proteasome. J. Mol. Biol. 326, 1437-48