Figure 8. Collapse model for vesicle tethering at the TGN.
Previous models based on GMAP-210 have led to a model that tethers extend from the Golgi as highly rigid rods that may bend in the middle ('Rigid hinge'). Data presented here show that GCC185 is shorter than originally predicted (145 nm vs. >204 nm), has splayed ends that can capture vesicles, and an unusual central bubble and floppiness as detected by atomic force microscopy. These features lead us to propose a flexible collapse model whereby the tether may collapse onto the Golgi surface, possibly facilitated by Rab GTPases and other proteins that are localized there. Note that vesicles may also (or alternately) bind near the bubble, and engage both the AP1 and Rab9 binding sites there, in addition to GCC185’s N-terminal arms.