SUCCESSIVE ACTION OF ESCHERICHIA-COLI CHAPERONES IN-VIVO

Escherichia coli DnaK, DnaJ and GrpE are required for renaturation of heat-inactivated lambda CI857 repressor (Gaitanaris ef at, 1990). Here we demonstrate that in addition to the above three proteins, GroEL an d GroES are necessary for the CI857 repressor to acquire full activity at the permissive temperature. Although full-length soluble repressor is present at normal amounts, the protein has reduced specific activi ty and migrates abnormally on native gels. To determine where the diff erent chaperones act in protein folding, we identified their cellular locations. DnaK and DnaJ are associated with nascent polypeptide chain s in translating ribosomes. In contrast, GroEL, although it is transie ntly associated with newly synthesized proteins, is absent from the ri bosomes. This suggests that DnaK and DnaJ play an early role in protei n maturation, whereas GroEL acts at a later stage.