A CISTERNAL MATURATION MECHANISM CAN EXPLAIN THE ASYMMETRY OF THE GOLGI STACK

Morphological data suggest that Golgi cisternae form at the cis-face o f the stack and then progressively mature into trans-cisternae. Howeve r, other studies indicate that COPI vesicles transport material betwee n Golgi cisternae, These two observations can be reconciled by assumin g that cisternae carry secretory cargo through the stack in the antero grade direction, while COPI vesicles transport Golgi enzymes in the re trograde direction, This model provides a mechanism for cisternal matu ration, If Golgi enzymes compete,vith one another for packaging into C OPI vesicles, we can account for the asymmetric distribution of enzyme s across the stack. (C) 1997 Federation of European Biochemical Societ ies.