Reconstitution in vitro of a membrane-fusion event involved in constitutive exocytosis. A role for cytosolic proteins and a GTP-binding protein, but not for Ca2+.

The fusion of post-Golgi transport vesicles with the plasma membrane is perhaps the least well understood step in the network of intracellular membrane traffic. We have used an 'in vitro' system to study this membrane-fusion event. We show here that fusion requires the presence of cytosolic proteins, but not Ca2+, and is inhibited by the non-hydrolysable GTP analogue guanosine 5'-[gamma-thio]triphosphate, which indicates the involvement of a GTP-binding protein.