THE CLP ATPASES DEFINE A NOVEL CLASS OF MOLECULAR CHAPERONES

The Clp ATPases were originally identified as a regulatory component o f the bacterial ATP-dependent Clp serine proteases. Proteins homologou s to the Escherichia coli Clp ATPases (ClpA, B, X or Y) have been iden tified in every organism examined so far. Recent data suggest that the Clp ATPases are not only specificity factors which help to 'present' various protein substrates to the ClpP or other catalytic proteases, b ut are also molecular chaperones which can function independently of C lpP. This review discusses the recent evidence that the Clp ATPases ar e indeed molecular chaperones capable of either repairing proteins dam aged during stress conditions or activating the initiation proteins fo r Mu, lambda or P1 DNA replication. A mechanism is suggested to explai n how the Clp ATPases 'decide' whether to repair or destroy their prot ein substrates.