ON NEUROFILAMENT and NEUROTUBULE PROTEINS FROM HUMAN AUTOPSY TISSUE

Neurofilaments and neurotubules are the principal fibers of the mature normal neuron. In this study the protein subunits of these neurofibrils were isolated from human autopsy tissue, and compared by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, and by two dimensional peptide maps of the tryptic digest of these proteins labelled with 125 I. The α and the β monomers of neurotubule are related but distinct in their peptide maps, while the major neurofilament protein subunit (molecular weight, 50,000) is remarkably similar to β tubulin. The neurofilament fraction binds colchicine, but the specificity is not yet determined. Neurotubule and neurofilament are also similar in having minor proteins which coelectrophorese on the gels. These results suggest that neurofilament and neurotubule may share one or more protein subunits.