Monoclonal antibody directed against the 43 000 dalton v1 polypeptide from Torpedo marmorata electric organ

The acetylcholine receptor (AcChoR) plays an essential role at the vertebrate neuromuscular junction and in the fish electric organ: it mediates the opening of the post-synaptic ion channel by the neurotransmitter acetylcholine (AcCho). The supra-molecular organization of the AcChoR within the subsynaptic membrane is highly characteristic. In the course of the maturation of the cholinergic synapse during embryogenesis, the AcChoR molecules change from being diffusely distributed and metabolically labile to densely-packed and stable aggregates. A 43 000 dalton protein which is associated with the Torpedo electrocyte synapses and is present in membrane highly enriched in AcChoR (SDS-PAGE) has been postulated to be involved in the immobilization and stabilization of the AcChoR in the subsynaptic membrane. However, when analysed on two-dimensional isoelectric focusing-SDS-PAGE gels, the 43 000 dalton protein band was shown to be composed of three distinct spots referred to as v1, v2 and v3. The three polypeptides had different peptide maps. Furthermore, the subcellular localisation of the 43 000 dalton protein is not clearly established and contradictory conclusions, based on indirect evidence, have been drawn. Thus, a further investigation of the 43 000 dalton proteins appeared necessary. Monoclonal antibodies against the 43 000 dalton proteins were developed in CBA mice and characterized using the horseradish peroxidase immunoreaction as a screening assay. One of the monoclonal antibodies was directed exclusively against the v1 polypeptide. It reacted only with membrane fractions containing the v1 polypeptide and did not label the cytoplasmic fraction prepared from adult Torpedo electric organ.(ABSTRACT TRUNCATED AT 250 WORDS)