Low temperature or GroEL/ES overproduction permits growth of Escherichia coli cells lacking trigger factor and DnaK

Escherichia coli trigger factor (TF) and DnaK cooperate in the folding of newly synthesized proteins. The combined deletion of the TF-encoding tig gene and the dnaK gene causes protein aggregation and synthetic lethality at 30degreesC. Here we show that the synthetic lethality of DeltatigDeltadnaK52 cells is abrogated either by growth below 30degreesC or by overproduction of GroEL/GroES. At 23degreesC DeltatigDeltadnaK52 cells were viable and showed only minor protein aggregation. Overproduction of GroEL/GroES, but not of other chaperones, restored growth of DeltatigDeltadnaK52 cells at 30degreesC and suppressed protein aggregation including proteins greater than or equal to 60 kDa, which normally require TF and DnaK for folding. GroEL/GroES thus influences the folding of proteins previously identified as DnaK/TF substrates. (C) 2004 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.