Rab GTPases are essential regulators of membrane trafficking. We report crystal
structures of Rab28 in the active (GppNHp-bound) and inactive (GDP-3'P-bound)
forms at 1.5 and 1.1A resolution. Rab28 is a distant member of the Rab family.
While the overall fold of Rab28 resembles that of other Rab GTPases, it
undergoes a larger nucleotide-dependent conformational change than other members
of this family. Added flexibility resulting from a double-glycine motif at the
beginning of switch 2 might partially account for this observation. The
double-glycine motif, which is conserved in the Arf family, only occurs in Rab28
and Rab7B of the Rab family, and may have a profound effect on their catalytic
activities.
