Identification of two proteolipid antigens with different localization at torpedo neuromuscular synapses.

The cholinergic nerve terminals of Torpedo electric organ are a rich source of a hydrophobic protein, the mediatophore, which endows artificial membranes with a calcium dependent mechanism that translocates acetylcholine. An antiserum raised against purified mediatophore permitted the identification of two different proteolipids of 14 and 15 kDa molecular weight. Mediatophore activity paralleled the abundance of the 15 kDa proteolipid. Antibodies to this 15 kDa proteolipid were affinity purified and the distribution of this antigen was studied at neuromuscular junction, where it was only detected at nerve terminals. An antisynaptic vesicle monoclonal antibody was produced and used as a nerve terminal specific marker. Its binding pattern was very similar to that of anti 15 kDa proteolipid antibodies. Their distribution is markedly different from that of the 14 kDa proteolipid which is associated with Schwann cells and endothelium of blood capilliaries as shown using affinity purified antibodies to the 14 kDa proteolipid.