Tubulin slow axonal transport

Slow axonal transport involves primarily components of the cytoskeleton and its protein precursors. Slow transport can be resolved into two rates, one of less than lmm/day and one of several mm/day. Components traveling at the slower rate include tubulin and its associated proteins, along with a group of three other structural proteins known as the neurofilament triplet. Components traveling at the faster rate include some tubulin, as well as actin and various soluble enzymes. It has been noted that the rate of rapid transport is constant in an animal over a range of... 

Although these two rate components can be identified in all nerves examined to date, the rates and the precise compositions varies among nerve populations. For example, SCa and SCb are readily resolved as discrete waves moving down optic axons, but differences in rate are smaller in the motor axons of sciatic nerve so the two peaks overlap. Moreover, virtually all tubulin moves as a single peak in SCa in optic axons, but significant amounts of tubulin move at both SCa and SCb rates in sciatic motor axons [32]. In each nerve, certain polypeptides may be used to define the kinetics for a given slow component of axonal transport. For SCa, those signature polypeptides are the NF triplet proteins, while actin, clathrin and calmodulin serve a similar role for SCb. 

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