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Updated: Jul 20, 2026

Comparing the Affinity of GTPase-binding Proteins using Competition Assays
Published on: October 8, 2015
Involvement of GTP-binding "G" proteins in transport through the Golgi stack
P Melançon1, B S Glick, V Malhotra
1Department of Biochemistry, Stanford University, California 94305.
Abstract:
GTP gamma S irreversibly inhibits protein transport between successive compartments of the Golgi stack in a cell-free system. Fluoride, potentiated by the addition of aluminum ion, also causes a strong inhibition. These are hallmarks of the involvement of a guanine nucleotide-binding or regulatory "G" protein. Inhibition by GTP gamma S requires a cytosolic inhibitory factor that binds to Golgi membranes during inhibition. Preincubation experiments reveal that GTP gamma S blocks the function of acceptor Golgi but not donor Golgi membranes. More specifically, a processing step in between vesicle attachment and the actual fusion event seems to be affected. Electron microscopy demonstrates a corresponding 5-fold accumulation of non-clathrin-coated buds and vesicles associated with the Golgi cisternae during inhibition by GTP gamma S.
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