<p>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 homologous to eubacterial HslV (ClpQ) and HslU (ClpY, clpX) have also been demonstrated in to be present in the genome of trypanosomatid protozoa [<cite idref="PUB00011906"/>].</p><p>The proteasome (or macropain) (<db_xref db="EC" dbkey="3.4.25.1"/>) [<cite idref="PUB00000524"/>, <cite idref="PUB00000148"/>, <cite idref="PUB00004123"/>, <cite idref="PUB00001329"/>, <cite idref="PUB00005460"/>] is a eukaryotic andarchaeal multicatalytic proteinase complex that seems to be involved inan ATP/ubiquitin-dependent nonlysosomal proteolytic pathway. In eukaryotes theproteasome is composed of about 28 distinct subunits which form a highlyordered ring-shaped structure (20S ring) of about 700 kDa.Most proteasome subunits can be classified, on the basis on sequencesimilarities into two groups, alpha (A) and beta (B).</p><p>The prokaryotic ATP-dependent proteasome is coded for by the heat-shock locus VU (HslVU). It consists of HslV, the protease (MEROPS peptidase subfamily T1B), and HslU, <db_xref db="INTERPRO" dbkey="IPR004491"/>, the ATPase and chaperone belonging to the AAA/Clp/Hsp100 family. The crystal structure of <taxon tax_id="2336">Thermotoga maritima</taxon> HslV has been determined to 2.1-A resolution. The structure of the dodecameric enzyme is well conserved compared to those from <taxon tax_id="562">Escherichia coli</taxon> and <taxon tax_id="727">Haemophilus influenzae</taxon> [<cite idref="PUB00014349"/>, <cite idref="PUB00014350"/>].</p><p>This entry contains threonine peptidases and non-peptidase homologs belong to MEROPS peptidase family T1 (proteasome family, clan PB(T)). The family consists of the protease components of the archaeal and bacterial proteasomes and the alpha and beta subunits of the eukaryotic proteasome. </p>