DnaK response to expression of protein mutants is dependent on translation rate and stability

Chaperones play a central part in the quality control system in cells by clearing misfolded and aggregated proteins. The chaperone DnaK acts as a sensor for molecular stress by recognising short hydrophobic stretches of misfolded proteins. As the level of unfolded protein is a function of protein stability, we hypothesised that the level of DnaK response upon overexpression of recombinant proteins would be correlated to stability. Using a set of mutants of the lambda-repressor with varying thermal stabilities and a fluorescent reporter system, the effect of stability on DnaK response and protein abundance was investigated. Our results demonstrate that the initial DnaK response is largely dependent on protein synthesis rate but as the recombinantly expressed protein accumulates and homeostasis is approached the response correlates strongly with stability. Furthermore, we observe a large degree of cell-cell variation in protein abundance and DnaK response in more stable proteins. A survey of lambda-repressor mutants using a fluorescent reporter system reveals the chaperone DnaK response for protein quality control.

Automated summary

Chaperones play a crucial role in cellular quality control by removing misfolded and aggregated proteins. The chaperone DnaK responds to molecular stress by recognizing hydrophobic regions of misfolded proteins. This study found that the level of DnaK response is correlated to protein stability when overexpressing recombinant proteins. Additionally, stable proteins showed variability in protein abundance and DnaK response among cells.