Vesicle coat proteins, such as the archetypal clathrin and the coat protein complexes II and I (COPII and COPI, respectively) are molecular machines with two central roles: enabling vesicle formation, and selecting protein and lipid cargo to be packaged within them. Thus, coat proteins fulfil a central role in the homeostasis of the cell's endomembrane system and are the basis of functionally segregated compartments. COPI operates in retrieval from the Golgi to the endoplasmic reticulum (ER) and in intra-Golgi transport, and maintains ER- and Golgi-resident chaperones and enzymes where they belong. Several reports have also highlighted a role for COPI in endosomal transport and function, regulating lipid droplet homeostasis, mRNA transport and the breakdown of the nuclear envelope. COPI consists of seven core subunits α-COP, β’-COP, ε-COP, β-COP, δ-COP, γ-COP and ζ-COP (see poster). A cytoplasmic heptamer of these subunits – termed coatomer – is recruited en bloc to the membrane bilayer to form the COPI coat. The coat protein complex I (COPI) allows the precise sorting of lipids and proteins between Golgi cisternae and retrieval from the Golgi to the ER. This essential role maintains the identity of the early secretory pathway and impinges on key cellular processes, such as protein quality control. Here you can see a crystal structure of the COPI cargo sorting module from Saccharomyces cerevisiae in complex to a peptide (PBD code: 8HQV)

#molecularart .. #COPI ... #sorting ... #module ... #interaction ... #golgi ... #cargo ... #xray

Structure rendered with @proteinimaging and depicted with @corelphotopaint