 The COPII complex is a heterohexamer, but not closely related to the AP/TSET complexes.The individual proteins of the COPII complex are called SEC proteins, because they are encoded by genes identified in secretory mutants of yeast.One especially interesting aspect of COPII is that it can form typical spherical vesicles "and" tubules to transport large molecules like collagen precursors, which cannot fit inside typical spherical vesicles.