Chaperone properties of rHtrA proteins. a Refolding of urea-denatured α-glucosidase in the presence of rHtrA1 or rHtrA2. α-Glucosidase was denatured in urea and then renatured for 20 min by dilution of the denaturant as described under “Methods”, at a concentration of 0.07 µM in the absence of additional protein and in the presence of either 5 µM rHtrA1, 5 µM rHtrA2 or 5 µM DnaK. b Thermal aggregation of citrate synthase in the presence of rHtrA1 or rHtrA2. The kinetics of citrate synthase aggregation was determined by light scattering at 650 nm. Native citrate synthase was diluted to a final concentration of 0.8 µM at 44°C, as described under “Methods”, in the absence of additional protein (circles), or in the presence of 5 µM rHtrA1 (triangles), 5 µM rHtrA2 (squares) or 5 µM DnaK (crosses).