COPI-mediated protein and lipid sorting in the early secretory pathway

The major function of the secretory pathway of eukaryotes is to maintain th e compartmental organization of the endomembrane system and organelle-assoc iated functions by proper distribution of newly synthesized molecules. Prot ein and lipid transport is mediated by vesicular intermediates that connect the various organelles throughout this pathway. This principle enables the eukaryotic cell to actively sort proteins and lipids at every level of thi s route, in both the anterograde and the retrograde direction. Here, we dis cuss the molecular mechanisms of non-clathrin(COP I and COP II)-coated-vesi cle biogenesis and how transport vesicle formation is linked to protein and lipid sorting in the early secretory pathway.