<p> Most Clp ATPases form complexes with peptidase subunits and are involved in protein degradation, though some, such as ClpB, do not associate with peptidases and are involved in protein disaggregation [<cite idref="PUB00045432"/>]. This entry represents the C-terminal domain of Clp ATPases, often referred to as the D2-small domain, which forms a mixed alpha-beta structure. Compared with the adjacent AAA D1-small domain (<db_xref db="INTERPRO" dbkey="IPR003959"/>) it lacks the long coiled-coil insertion, and instead of helix C4 contains a beta-strand (e3) that is part of a three stranded beta-pleated sheet. In Thermophilus the whole protein forms a hexamer with the D1-small and D2-small domains located on the outside of the hexamer, with the long coiled-coil being exposed on the surface. The D2-small domain is essential for oligomerisation, forming a tight interface with the D2-large domain of a neighbouring subunit, thereby providing enough binding energy to stabilise the functional assembly [<cite idref="PUB00030406"/>].</p>