Large ARF guanine nucleotide exchange factors in membrane trafficking.

In eukaryotic cells membrane compartments are connected through cargo-selective vesicle trafficking mediating the exchange of components between different organelles. This exchange is essential to maintain their structural integrity and specific composition. A fundamental regulatory step in vesicle formation is the activation of small ARF GTPases by exchanging their bound GDP for GTP, which is a prerequisite for ARF-mediated effector recruitment. Activation of ARFs is catalyzed by the characteristic SEC7 domain of guanine nucleotide exchange factors (ARF-GEFs), which are classified according to their additional protein domains.The only group of ARF-GEFs conserved in mammals, yeast and plants are the large ARF-GEFs. This review summarizes recent findings on the function of large ARF-GEFs, and the use of the inhibitor Brefeldin A as a potent tool in understanding membrane trafficking. Furthermore we highlight common themes and apparent differences in large ARF-GEF function between eukaryotic kingdoms.