Single-molecule analysis of a molecular disassemblase reveals the mechanism of Hsc70-driven clathrin uncoating

Heat shock cognate protein-70 (Hsc70) supports remodeling of protein complexes, such as disassembly of clathrin coats on endocytic coated vesicles. To understand how a simple ATP-driven molecular clamp catalyzes a large-scale disassembly reaction, we have used single-particle fluorescence imaging to track the dynamics of Hsc70 and its clathrin substrate in real time. Hsc70 accumulates to a critical level, determined by kinetic modeling to be one Hsc70 for every two functional attachment sites; rapid, all-or-none uncoating then ensues. We propose that Hsc70 traps conformational distortions, seen previously by cryo-EM, in the vicinity of each occupied site and that accumulation of local strains destabilizes the clathrin lattice. Capture of conformational fluctuations may be a general mechanism for chaperone-driven disassembly of protein complexes.