Structure of an auxilin-bound clathrin coat and its implications for the mechanism of uncoating

• Published in: Nature Vol. 432; no. 7017; pp. 649 - 653
• Main Authors: Kirchhausen, Tomas, Fotin, Alexander, Cheng, Yifan, Grigorieff, Nikolaus, Walz, Thomas, Harrison, Stephen C
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 02.12.2004; Nature Publishing Group
• Subjects: Animals; Auxilins - chemistry; Auxilins - genetics; Auxilins - metabolism; Auxilins - ultrastructure; Biological and medical sciences; Cattle; Cells; Clathrin - chemistry; Clathrin - metabolism; Clathrin - ultrastructure; Clathrin Heavy Chains - chemistry; Clathrin Heavy Chains - metabolism; Clathrin Heavy Chains - ultrastructure; Cryoelectron Microscopy; Fundamental and applied biological sciences. Psychology; HSC70 Heat-Shock Proteins; HSP70 Heat-Shock Proteins - metabolism; Models, Molecular; Molecular and cellular biology; Molecular biology; Peptide Fragments - chemistry; Peptide Fragments - metabolism; Peptide Fragments - ultrastructure; Protein Binding; Protein Conformation; Proteins; Structure-Activity Relationship; Membrane; Clathrin; Chaperone; Mechanism; Structural analysis
• DOI: 10.1038/nature03078
• ISSN: 0028-0836

Clathrin-coated pits invaginate from specific membrane compartments and pinch off as coated vesicles. These vesicles then uncoat rapidly once released. The Hsc70 molecular chaperone effects the uncoating reaction, and is guided to appropriate locations on clathrin lattices by the J-domain-containing co-chaperone molecule auxilin. This raises the question of how a local event such as ATP hydrolysis by Hsc70 can catalyse a global disassembly. Here, we have used electron cryomicroscopy to determine 12-Å-resolution structures of in-vitro-assembled clathrin coats in association with a carboxy-terminal fragment of auxilin that contains both the clathrin-binding region and the J domain. We have located the auxilin fragment by computing differences between these structures and those lacking auxilin (described in an accompanying paper). Auxilin binds within the clathrin lattice near contacts between an inward-projecting C-terminal helical tripod and the crossing of two 'ankle' segments; it also contacts the terminal domain of yet another clathrin 'leg'. It therefore recruits Hsc70 to the neighbourhood of a set of critical interactions. Auxilin binding produces a local change in heavy-chain contacts, creating a detectable global distortion of the clathrin coat. We propose a mechanism by which local destabilization of the lattice promotes general uncoating.