Anti-canine Rab9 (mouse) antibody

We have recently shown that rab9 plays a key role in the transport of proteins between late endosomes and the trans Golgi network. Purified, recombinant, rab9 protein stimulated transport in a cell free system that reconstitutes this event. Using gel filtration chromatography, we show that like other small GTP binding proteins, cytosolic rab9 occurs as an 80-kD complex with a GDI-like protein. Purified, recombinant rab9 protein could also be assembled into 80-kD complexes in vitro, as long as the protein possessed an intact carboxy-terminus and had been incubated under conditions which favor prenylation. Moreover, prenylated rab9 could be shown to form an equimolar complex with authentic rab3A-GDI. Finally, rab3A-GDI had the capacity to dissociate the GDP form of prenylated rab9 protein from cellular membranes. These findings support a role for GDI proteins in the solubilization and recycling of rabs from their target membranes, at the end of a rab protein-mediated catalytic cycle.