On the Logic of Golgi's Apparatus-Continuous Purification of Proteins in the Cell

All eukaryotic cells have a Golgi apparatus, consisting of a series of stacked membrane-bounded compartments (termed cisternae). The Golgi apparatus plays a central role in the processing and distribution of newly synthesized proteins. The purpose of the stack-like morphology has long been a mystery. In this lecture I will develop the idea, first proposed in the 1980s, that the stack carries out a process of protein purification, separating proteins destined to remain in the endoplasmic reticulum (and the Golgi itself) from other locations. In this process of iterative protein sorting, the same purification process occurs sequentially at each level of the stack, resulting in high overall efficiencies. The cisternae function as if they were plates in a distillation tower in solvent separations. The details of the process are still debated. Retrograde flow is mediated by typical transport vesicles. Anterograde flow may be mediated by movement of intact cisternae or by vesicle-like carriers. Recent evidence emerging from synthetic biology - in which we have deliberately altered the adhesive properties of the cisternae to each other and to other organelles - will be presented.