InterPro domain: IPR019489

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 [ 1 ]. 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 ( 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 [ 2 ].

1. A camel passes through the eye of a needle: protein unfolding activity of Clp ATPases. Mol. Microbiol. 61, 1094-100
2. The structure of ClpB: a molecular chaperone that rescues proteins from an aggregated state. Cell 115, 229-40