Fig. 4. Immunogold detection of the V-ATPase subunit c in a freeze-fractured nerve ending. A typical nerve terminal, frozen in situ in the electric organ, was fractured and replicated. The fracture plane crosses the nerve terminal cytoplasm (right), which contains many synaptic vesicles (arrowheads). It splits the plasma membrane (left), exhibiting a large surface area of the presynaptic membrane E face. Binding of mAb 15K1 to the VATPase c subunit embedded in the replica was indirectly visualized using anti-mouse Ig antibodies conjugated to 15 nm gold particles (arrows).