The Golgi apparatus: roles for distinct 'cis' and 'trans' compartments.

The Golgi apparatus seems to consist of distinct cis and trans compartments that are proposed to act sequentially to refine the protein export of the endoplasmic reticulum by removing escaped endoplasmic reticulum proteins. Refinement may be a multi-stage process that employs a principle akin to fractional distillation; the stack of cisternae comprising the cis Golgi may be the plates in this distillation tower. The trans Golgi, consisting of the last one or two cisternae, may be the receiver that collects from the cis Golgi only its most refined fraction for later distribution to specific locations throughout the cell.