Functional Modules

    Barbed End Capping[Edit]

    Figure 1. Capping proteins promote actin filament disassembly: (A) Protrusion of filopodia or lamellipodia is dependent upon actin polymerization at the barbed end of actin filaments. (B) Capping proteins bind to existing actin filaments at the barbed end to prevent filament assembly.(C) ADP-actin continues to depolymerize from the pointed end of the actin filaments. When all of the actin filaments are capped in a filopodium, protrusion is prevented and filament disassembly is favored.
    Barbed end capping is essential for efficient disassembly of pointed ends. Capping proteins prevent annealing of severed or debranched filaments and they block both the association and dissociation of subunits at the barbed end [1]. Capping proteins are not only required for profilin to sequester ATP–actin monomers [2], but capping proteins and profilin cooperate to depolymerize filaments faster because of severing and enhanced ADP-actin dissociation from pointed ends [3].


    References

    1. Narita A., Takeda S., Yamashita A., Maéda Y. Structural basis of actin filament capping at the barbed-end: a cryo-electron microscopy study. EMBO J. 2006; 25(23). [PMID: 17110933]
    2. Pantaloni D., Carlier MF. How profilin promotes actin filament assembly in the presence of thymosin beta 4. Cell 1993; 75(5). [PMID: 8252614]
    3. Blanchoin L., Pollard TD., Mullins RD. Interactions of ADF/cofilin, Arp2/3 complex, capping protein and profilin in remodeling of branched actin filament networks. Curr. Biol. 2000; 10(20). [PMID: 11069108]
    Updated on: Wed, 26 Feb 2014 10:53:23 GMT
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