Tubulin distribution along the torpedo electromotoneuron, an immunochemical study

Abstract The tubulin concentration along the Torpedo electromotoneuron was estimated using a new monoclonal anti-tubulin antibody (mAb 140.2). The highest level of tubulin was associated with the proximal portion of the axon (4.8 mg/ml); intermediate levels were found in the distal axon (2.7 mg/ml) and at the level of the cell bodies, while a purified preparation of nerve terminals contained only low amounts of tubulin (1.1 mg/ml). Similar results were obtained using immunohistochemical localization of tubulin. While preterminal branches were brightly stained, the nerve terminal field remained unstained. These observations are consistent with the hypothesis that cytoskeletal components are degraded upon reaching the nerve terminals. Indeed, the appearance of lower molecular weight polypeptides recognized by the mAb 140.2 was striking in the distal portions of the nerve.