Abstract
The heat shock protein 70 molecular chaperone system of DnaK, DnaJ and GrpE is necessary for the replication of several E. coli phage and plasmids. For plasmid P1 DNA replication, this system activates DNA binding by the initiator protein, RepA. Activation exposes the DNA binding domain of RepA through the conversion of RepA dimers to monomers. In apparent contrast, the chaperones act after the assembly of the preprimosomal complex for phage λ DNA replication. They remodel and rearrange the proteins within the complex to activate the DnaB helicase. The mechanism of action of DnaK, DnaJ and GrpE is, however, very likely similar in both of these systems. Members of a new chaperone family, ClpA and ClpX, activate the DNA replication initiator proteins of plasmid P1 and phage λ, respectively. They also function in the ATP-dependent degradation of these proteins in conjunction with ClpP peptidase.
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