Figure 2.

Stimulation of DnaK ATPase by DnaJ requires protein substrate. (A) Effects of DnaJ, DnaJ259, σ³², and unfolded luciferase (final concentrations indicated) on ATP hydrolysis rates of DnaK as determined by single-turnover assays. Luciferase was unfolded in 3 M Gdn⋅HCl and diluted into refolding buffer. The final Gdn⋅HCl concentration (180 mM) had no effect on unstimulated and DnaJ-stimulated hydrolysis rates (data not shown). (B) Effects of increasing σ³² and peptide substrate [σ³²-Q132-Q144 (28)] on ATP hydrolysis rates of DnaK in the presence of DnaJ. The ATP hydrolysis rates were determined in standard single-turnover assays.