Cohesive axonal transport of the slow component b complex of polypeptides

Abstract

The axonal transport of the diverse group of polypeptides characteristic of slow component b (SCb), or Group IV, may be accomplished either by a bulk flow mechanism acting on each of the individual polypeptides or by their movement through the axoplasm as part of a physical complex or structural assembly. In order to determine if the SCb polypeptides travel as a cohesive unit (which would be consistent with the latter alternative above), we examined in detail the quantitative distribution of the individual SCb polypeptides in the guinea pig optic system at three different times after pulse radiolabeling the neuron cell bodies. Eighteen SCb polypeptides were selected as appropriate for analysis. Individual optic systems at the three select times after labeling were harvested, cut into small segments, and subjected to SDS-PAGE. Individual radioactive polypeptide bands were identified and located by fluorography, excised, and then quantified by scintillation counting.