Structure of clathrin coat with bound Hsc70 and auxilin: mechanism of Hsc70-facilitated disassembly.
The chaperone Hsc70 drives the clathrin assembly-disassembly cycle forward by stimulating dissociation of a clathrin lattice. A J-domain containing co-chaperone, auxilin, associates with a freshly budded clathrin-coated vesicle, or with an in vitro assembled clathrin coat, and recruits Hsc70 to its specific heavy-chain-binding site. We have determined by electron cryomicroscopy (cryoEM), at about 11 A resolution, the structure of a clathrin coat (in the D6-barrel form) with specifically bound Hsc70 and auxilin. The Hsc70 binds a previously analysed site near the C-terminus of the heavy chain, with a stoichiometry of about one per three-fold vertex. Its binding is accompanied by a distortion of the clathrin lattice, detected by a change in the axial ratio of the D6 barrel. We propose that when Hsc70, recruited to a position close to its target by the auxilin J-domain, splits ATP, it clamps firmly onto its heavy-chain site and locks in place a transient fluctuation. Accumulation of the local strain thus imposed at multiple vertices can then lead to disassembly.
Xing
Yi
Y
Department of Biological Chemistry and Molecular Pharmacology, Jack and Eileen Connors Structural Biology Laboratory, Harvard Medical School, Boston, MA 02115, USA.
Böcking
Till
T
Wolf
Matthias
M
Grigorieff
Nikolaus
N
Kirchhausen
Tomas
T
Harrison
Stephen C
SC
D000818:Animals; D034021:Auxilins / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D002966:Clathrin / Q000737:chemistry / Q000378:metabolism*; D022163:Clathrin-Coated Vesicles / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D050883:HSC70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary
D034021:Auxilins; D002966:Clathrin; D050883:HSC70 Heat-Shock Proteins; D046912:Multiprotein Complexes