Molecular model of a complete clathrin lattice. The polyhedral protein lattice coats eukaryotic cell membranes (vesicles) and coated pits and appears to be involved in protein secretion and membrane trafficking. This protein also occurs in synaptic vesicles. The fibrous protein forms a characteristic polyhedral coat on the surface of coated pits and coated vesicles. Clathrin-coated vesicles are important vehicles of membrane traffic in cells