Fig. 2
Effect of trigger factor on the folding properties of protein L under force. a Representative force-clamp magnetic tweezers trajectory of a protein L octamer in presence of 500 μM TF with the monitored properties highlighted. After the unfolding pulse, the molecule is set at a constant force (8.1 pN in this case), relaxing to an equilibrium state. The kinetic properties are reflected in the first passage time (FPT), time taken to, starting with all domains unfolded, fold the eight domains for the first time (time between arrows, highlighted). In equilibrium, the molecule experiences several folding-unfolding transitions, reflected in different residence times at each folding state (labeled as the number of folded domains), marked with the dashed blue lines. The folding probability is calculated by monitoring the fraction of time spent on each of the states (black bars). b Mean-FPT for total refolding in presence (red) and absence (black) of TF. TF modulates the folding kinetics by speeding up the time needed to refold all eight domains. Above 7.4 pN, a protein L octamer needs over 1000 s to fold completely, while TF accelerates folding over an order of magnitude. Each data point represents the average of more than ten experiments. Error bars represent s.e.m. c Folding probability in presence (red) and absence (black) of TF. The presence of the molecular chaperone TF increases considerably the folding probability over the range from 7 to 10 pN. The inset shows the relative increment, reaching up to 40%. Data points are calculated as described above, using >3000 s, and over more than three molecules per force. Errors bars are s.e.m
