Purification and characterization of Rab GDI beta from rat brain.

A new Rab GDI was purified from the synaptic soluble fraction of rat brain by several column chromatographies as a protein that inhibited the dissociation of [3H]GDP from Rab3A but was not recognized by an anti-Rab GDI alpha antibody. The partial amino acid sequence analysis revealed that it was identical with rat Rab GDI beta. Purified Rab GDI beta showed the kinetic properties similar to those of Rab GDI alpha, including the inhibitory effect on the dissociation of GDP from Rab3A, the substrate specificity, the requirement of the post-translational lipid modifications of Rab3A, the stoichiometric interaction with the GDP-bound form of Rab3A, the inhibitory effect on the binding of Rab3A to erythrocyte ghosts, and the stimulatory effect on the dissociation of Rab3A from the membrane.