Physical interaction between heat shock proteins DnaK, DnaJ, and GrpE and the bacterial heat shock transcription factor sigma 32.

Genetic evidence indicates central roles for Hsp70 chaperones in the regulation of heat shock gene expression. This regulatory function has been postulated for Escherichia coli to rely on the direct association of DnaK (Hsp70) with the heat shock transcription factor sigma 32. This report presents evidence for the physical association of DnaK, DnaJ, and GrpE chaperones with sigma 32 in vivo. Surprisingly, an interaction of DnaJ with sigma 32 exists that is distinguishable from an interaction of DnaK and GrpE with sigma 32: addition of ATP disrupts the association of DnaK and GrpE with sigma 32, but not the association of DnaJ with sigma 32. Furthermore, DnaJ-sigma 32 and DnaK-sigma 32 associations occur independent of DnaK and DnaJ, respectively. These results suggest distinct regulatory functions of DnaJ and DnaK/GrpE.