Clathrin is the major protein of the polyhedral coat of coated pits and vesicles which entrap specific macromolecules during receptor-mediated endocytosis. The clathrin molecule has a triskelion shape. Each clathrin triskelion is composed of three identical heavy chains (180 kDa) and three light chains of two types,LCA (CLTA) and LCB (CLTB) (30-40 kDa). The light chain subunits are thought to regulate the formation or disassembly of clathrin coats.