VACUOLAR H-ATPASE DOMAINS ARE TRANSPORTED SEPARATELY IN AXONS AND ASSEMBLE IN TORPEDO NERVE-ENDINGS()

Torpedo electric organ synaptosomes possess a typical vacuolar H+-ATPa se (V-ATPase), inhibited by concanamycin A and insensitive to vanadate , made of the association of a catalytic soluble sector V-1 to a membr ane domain V-0. In the electric nerves, the 57-kDa subunit B of the V- 1 sector was transported to the nerve endings by the slow axonal flow and did not accumulate upstream from an axonal block. In contrast, a 5 00% accumulation of the 15-kDa subunit c of the V-0 membrane domain wa s observed, demonstrating that this subunit is conveyed by the fast ax onal anterograde transport. After velocity sedimentation of solubilize d nerve proteins, the 57- and 15-kDa subunits were recovered in differ ent complexes corresponding, respectively, to the V-1 and V-0 domains. No fully assembled V-ATPase was detected. It is concluded that V-1 an d V-0 domains of V-ATPase are transported separately in axons, at diff erent rates,and that they only associate once arrived in nerve endings to form the active V-ATPase.