SPONTANEOUS-CURVATURE THEORY OF CLATHRIN-COATED MEMBRANES

Clathrin-coated membranes are precursors to coated vesicles in the rec eptor-mediated endocytic pathway. In this paper we present a physical model for the first steps of the transformation of a clathrin-coated m embrane into a coated vesicle. The theory is based on in vitro cytopla smic acidification experiments of Heuser (J. Cell Biol. 108:401-411) t hat suggest the transformation proceeds by changes in the chemical env ironment of the clathrin lattice, wherein the chemical environment det ermines the amount of intrinsic, or spontaneous, curvature of the netw ork. We show that a necessary step of the transformation, formation of free pentagons in the clathin network, can proceed via dislocation un binding, driven by changes in the spontaneous curvature. Dislocation u nbinding is shown to favor formation of coated vesicles that are quite small compared to those predicted by the current continuum theories, which do not include the topology of the clathrin lattice.