Family

Proteasome B-type subunit (IPR023333)

Short name: Proteasome_suB-type

Family relationships

Description

ATP-dependent protease complexes are present in all three kingdoms of life, where they rid the cell of misfolded or damaged proteins and control the level of certain regulatory proteins. They include the proteasome in Eukaryotes, Archaea, and Actinomycetales and the HslVU (ClpQY, clpXP) complex in other eubacteria. Genes homologues to eubacterial HslU (ClpY, clpX) have also been demonstrated in to be present in the genome of trypanosomatid protozoa [PMID: 12446803].

The proteasome (or macropain) (EC:3.4.25.1) [PMID: 7682410, PMID: 2643381, PMID: 1317508, PMID: 7697118, PMID: 8882582] 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 700 kDa. 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 [PMID: 9087403]. 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") [PMID: 2535672]. The proteasome subunits are related to N-terminal nucleophile hydrolases, and the catalytic subunits have an N-terminal threonine nucleophile.

The prokaryotic ATP-dependent proteasome is coded for by the heat-shock locus VU (HslVU). It consists of HslV, a peptidase, and HslU (IPR004491), the ATPase and chaperone belonging to the AAA/Clp/Hsp100 family. The crystal structure of Thermotoga maritima HslV has been determined to 2.1-A resolution. The structure of the dodecameric enzyme is well conserved compared to those from Escherichia coli and Haemophilus influenzae [PMID: 12646382, PMID: 12823960].

This family consists of the beta (or B type) subunits of the eukaryotic proteasome as well as the archaeal and bacterial proteasomes. These proteins belong to family T1 in the classification of peptidases.

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004298 threonine-type endopeptidase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE profiles