Figure 7. Transition of Hsc70-loaded coats to the disassembly phase.

(a) Experimental design used for the pH shift experiment. After immobilization of the clathrin/AP-2 coats onto the modified coverslip, the microfluidic chamber was perfused sequentially with auxilin, and then with a mixture of auxilin and Hsc70-AF568–ATP at pH 6. At this pH, the coats do not dissociate ²³. To trigger uncoating, the pH was shifted to 6.8 in the presence of unlabeled Hsc70–ATP. Minimal uncoating was observed if the pH shift was done in the absence of Hsc70–ATP. (b) Histogram of the dwell times between pH shift and initiation of disassembly. The distribution of dwell times is a single exponential, indicating that the transition of an Hsc70-loaded coat to the disassembly phase has a single rate-limiting step, with rate constant k₂⁺ (0.16 s⁻¹).