The Escherichia coli DjlA and CbpA can substitute for DnaJ in DnaK-mediated protein disaggregation

The DnaJ (Hsp40) protein of Escherichia coli serves as a cochaperone of DnaK (Hsp70), whose activity is involved in protein folding, protein targeting for degradation, and rescue of proteins from aggregates. Two other E. coli proteins, CbpA and DjIA, which exhibit homology with DnaJ, are known to interact with DnaK and to stimulate its chaperone activity. Although it has been shown that in dnaJ mutants both CbpA and DjIA are essential for growth at temperatures above 37degreesC, their in vivo role is poorly understood. Here we show that in a dnaJ mutant both CbpA and DjIA are required for efficient protein dissaggregation at 42degreesC.