A structure of the COPI coat and the role of coat proteins in membrane vesicle assembly

A coat of many components The formation of coated trafficking vesicles is among the most fundamental of cellular processes. COP1 transport vesicles are involved in retrograde membrane trafficking in the Golgi apparatus and endoplasmic reticulum. Dodonova et al. applied cryo–electron tomography to determine the structure of the COPI coat in its fully assembled form on budded vesicles (see the Perspective by Noble and Stagg). They combined structural data with cross-linking mass spectrometry to generate a complete molecular model. The model suggests a mechanism of coat assembly in which coat proteins cluster via flexible interactions instead of forming a protein cage on the membrane. Science , this issue p. 195 ; see also p. 142