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  • The EMBO Journal (2003) 22, 4980 - 4990
  • doi:10.1093/emboj/cdg511

Clathrin self-assembly involves coordinated weak interactions favorable for cellular regulation

Diane E. Wakeham1,2, Chih-Ying Chen1, Barrie Greene1,3, Peter K. Hwang4 and Frances M. Brodsky1,2

  1. The G. W. Hooper Foundation, Department of Microbiology and Immunology, Department of Biopharmaceutical Sciences and Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143-0552, USA
  2. Graduate Program in Chemistry and Chemical Biology, University of California, San Francisco, CA 94143-0552, USA
  3. Present address: Incyte Corporation, 3160 Porter Drive, Palo Alto, CA 94304, USA
  4. Macromolecular Structure Group, University of California, San Francisco, CA 94143-0552, USA

Correspondence to:

Frances M. Brodsky, E-mail: fmarbro@itsa.ucsf.edu

Received 29 November 2002; Accepted 14 August 2003; Revised 14 August 2003

The clathrin triskelion self-assembles into a polyhedral coat surrounding membrane vesicles that sort receptor cargo to the endocytic pathway. A triskelion comprises three clathrin heavy chains joined at their C-termini, extending into proximal and distal leg segments ending in a globular N-terminal domain. In the clathrin coat, leg segments entwine into parallel and anti-parallel interactions. Here we define the contributions of segmental interactions to the clathrin assembly reaction and measure the strength of their interactions. Proximal and distal leg segments were found to lack sufficient affinity to form stable homo- or heterodimers under assembly conditions. However, chimeric constructs of proximal or distal leg segments, trimerized by replacement of the clathrin trimerization domain with that of the invariant chain protein, were able to self-assemble in reversible reactions. Thus clathrin assembly occurs because weak leg segment affinities are coordinated through trimerization, sharing a dependence on multiple weak interactions with other biopolymers. Such polymerization is sensitive to small environmental changes and is therefore compatible with cellular regulation of assembly, disassembly and curvature during formation of clathrin-coated vesicles.

  • Keywords:

    • assembly,
    • clathrin,
    • cooperativity,
    • curvature,
    • trimerization