Schematic representation of a stacked Golgi apparatus that undergoes cisternal maturation.

<p>A) ER-derived vesicles (beige) fuse with each other to yield the first, most <i>cis</i>, cisterna. Individual cisterna mature from position 1 to position 8, where they disintegrate into transport carriers destined for the plasma membrane and endosomes. Vesicles originating from cisterna #2 deliver <i>cis</i> Golgi proteins to cisterna #1 while at the same time cisterna #2 receives Golgi resident proteins from cisterna #3. B) The cisternae are categorized as <i>cis</i>, medial and <i>trans</i> based on the abundance of Golgi residence proteins, mostly glycosylating enzymes, which exhibit distinct but overlapping peaks along the Golgi stack according to their sequential role in the processing of exocytic cargo. C) Two SNARE pairs, which we term SNARE (purple) and SNARE (green) are thought to mediate intra-Golgi transport of resident proteins. The respective v and t-SNAREs of SNARE both decay with a steep gradient from <i>cis</i> to <i>trans</i>. -t-SNAREs decay with a shallow gradient, while its corresponding -v-SNARE concentration increases from cisternae 1 to 8. The graphs are schematic representations of data from <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003125#pcbi.1003125-Volchuk1" target="_blank">[17]</a>.