InterPro domain: IPR037555

The proteasome (or macropain) ( 3.4.25.1 ) is a multicatalytic proteinase complex in eukaryotes and archaea, and in some bacteria, that is involved in an ATP/ubiquitin-dependent non-lysosomal proteolytic pathway [ 1 , 2 , 3 , 4 , 5 ]. In eukaryotes the 20S proteasome is composed of 28 distinct subunits which form a highly ordered ring-shaped structure (20S ring) of about 700kDa. Proteasome subunits can be classified on the basis of sequence similarities into two groups, alpha (A) and beta (B). The proteasome consists of four stacked rings each composed of only alpha or beta subunits, the rings are stacked in the order alpha/beta/beta/alpha. There are seven different alpha subunits and seven different beta subunits [ 6 ].

This entry contains the proteasome subunit known as alpha 3 in animals and alpha type 7 in fungi (MEROPS identifier T01.977). This is a non-proteolytic component of the 20S core proteasome complex. By itself, alpha 3 will form a homoheptameric ring, and can induce its neighbouring subunits in the alpha ring to form heteroheptamic complexes if co-expressed [ 7 ].

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6. Structure of 20S proteasome from yeast at 2.4 A resolution. Nature 386, 463-71
7. The human proteasomal subunit HsC8 induces ring formation of other alpha-type subunits. J. Mol. Biol. 275, 113-21