IMMUNOGOLD LOCALIZATION OF THE DNAK HEAT-SHOCK PROTEIN IN ESCHERICHIA-COLI-CELLS

Previously reported cell fractionation experiments have yielded conflicting information on the cellular localization of the DnaK heat shock protein of Escherichia coli. Here we used immunogold labelling of ultra-thin sections to determine the localization of DnaK in unstressed cells at 30-degrees-C as well as in heat-shocked cells. In cells grown at 30-degrees-C, gold particles were found predominantly in the cytoplasm, indicating that the majority of the DnaK molecules are cytoplasmic; however, a fraction of the gold particles was located in proximity to the membranes, raising the possibility that a subpopulation of DnaK proteins is membrane-associated. Heat shock of the cells did not induce detectable relocalization of DnaK.