InterPro domain: IPR024372

The proteasome (or macropain) ( 3.4.25.1 ) [ 1 , 2 , 3 , 4 , 5 ] 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. 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 composed of alpha/beta/beta/alpha subunits. There are seven different alpha subunits and seven different beta subunits [ 6 ]. Three of the seven beta subunits are peptidases, each with a different specificity. Subunit beta1c (MEROPS identifier T01.010) has a preference for cleaving glutaminyl bonds ("peptidyl-glutamyl-like" or "caspase-like"), subunit beta2c (MEROPS identifier T01.011) has a preference for cleaving arginyl and lysyl bonds ("trypsin-like"), and subunit beta5c (MEROPS identifier T01.012) cleaves after hydrophobic amino acids ("chymotrypsin-like") [ 7 ]. The proteasome subunits are related to N-terminal nucleophile hydrolases, and the catalytic subunits have an N-terminal threonine nucleophile.

Ecm29 is an adapter/scaffolding protein that tethers the proteasome core particle to the regulatory particle, stabilising the interaction between these two components [ 8 , 9 , 10 ].

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