The role of DnaK/DnaJ and GroEL/GroES systems in the removal of endogenousproteins aggregated by heat-shock from Escherichia coli cells

The submission of Esccerichia coli cells to heat-shock (45 degrees C, 15 mi n) caused the intracellular aggregation of endogenous proteins, In the,vt c ells the aggregates (the S fraction) disappeared 10 min after transfer to 3 7 degrees C, In contrast, the S fraction in the dnaK and dnaJ mutant strain s was stable during approximately one generation time (45 min). This demons trated that neither the renaturation nor the degradation of the denatured p roteins was possible in the absence of DnaK and DnaJ, The groEL44 and groES 619 mutations stabilised the aggregates to a lesser extent. It was shown by the use of cloned genes, dnaK/dnaJ or groEL/groES, producing the correspon ding proteins in about 4-fold excess, that the appearance of the S fraction in the wt strain. resulted from a transiently insufficient supply of the h eat-shock proteins. Overproduction of the GroEL/GroES proteins in dnaK756 o r dnaJ259 background prevented the aggregation, however, overproduction of the DnaK/DnaJ proteins did not prevent the aggregation in the groEL44 or gr oES619 mutant cells although it accelerated the disappearance of the aggreg ates. The properties of the aggregated proteins are discussed from the poin t of view of their competence to renaturation/degradation by the heat-shock system. (C) 1999 Federation of European Biochemical Societies.