InterPro domain: IPR001270

This family belongs to the AAA+ (ATPase associated with diverse cellular activities) superfamily. Most of these proteins of this family (ClpA, ClpC, ClpD, ClpE, ClpX, HslU) are involved in proteolysis and associate with a separate proteolytic subunit (ClpP, HslV) to form the active protease. ClpB is not involved in proteolysis but rather acts in collaboration with the DnaK (Hsp70) chaperone system to disassemble and refold large protein aggregates.

A group of ATP-binding proteins that includes the regulatory subunit of the ATP-dependent protease clpA; heat shock proteins clpB, 104 and 78; and chloroplast proteins CD4a (ClpC) and CD4b belong to this family [ 1 , 2 ]. The proteins are thought to protect cells from stress by controlling the aggregation and denaturation of vital cellular structures. They vary in size, but share a domainwhich contains an ATP-binding site.

These signatures which span the ATP binding region also identify the bacterial DNA polymerase III subunit tau ( 2.7.7.7 ), ATP-dependent protease La ( 3.4.21.53 ) and the mitochondrial lon protease homologue ( 3.4.21 ), both of which belong to MEROPS peptidase family S16.

1. Hsp104 is a highly conserved protein with two essential nucleotide-binding sites. Nature 353, 270-3
2. Conservation of the regulatory subunit for the Clp ATP-dependent protease in prokaryotes and eukaryotes. Proc. Natl. Acad. Sci. U.S.A. 87, 3513-7