It is functionally necessary for rab 9, like other rab family members, to be prenylated by two 20-carbon geranylgeranyl groups at the C-terminus. Most prenylated rab 9 is membrane bound, however, 10-20% of the cellular pool of rab 9 is bound to GDP dissociation inhibitor-alpha (GDI-alpha) in the cytosol. GDI recycles prenylated, GDP bound rab 9 from their fusion targets back to their membranes of origin.