Prenylation of RabGTPases, their delivery to membranes, and rab recycling

Rab proteins, in common with many other Ras superfamily members, need to be lipidated (in the case of Rab geranylgeranylated) at their C-terminus to be able to interact with membranes. Here, we review the basic mechanism of geranlygeranylation and then address the still unsolved question of how prenylated Rabs are delivered to specific membranes. The evidence reviewed leads to a model in which specifically localized guanine nucleotide exchange factors are an essential component of the targeting mechanism, and that additional stabilizing interactions are important in a number of cases, including effector interactions and positively charged residues in the C-terminus in at least one case examined. Finally, there is evidence that in some cases additional still unidentified factors are involved.