Blackwell Publishing Journal Backfiles 1879-2005
Escherichia coli DnaK, DnaJ and GrpE are required for renaturation of heat-inactivated λ CI857 repressor (Gaitanaris et al., 1990). Here we demonstrate that in addition to the above three proteins, GroEL and 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 activity and migrates abnormally on native gels. To determine where the different chaperones act in protein folding, we identified their cellular locations. DnaK and DnaJ are associated with nascent polypeptide chains in translating ribosomes. In contrast, GroEL, although it is transiently associated with newly synthesized proteins, is absent from the ribosomes. This suggests that DnaK and DnaJ ptay an early role in protein maturation, whereas GroEL acts at a later stage.
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