Kinesin from pig brain studied by electron microscopy.

Kinesin, a protein that transports particles along microtubules, has been purified from pig brain, following published methods. By electron microscopy of both shadowed and negatively stained specimens, it appears to be a rod with a large branched structure at one end and a small fork at the other. The total length of the structure is about 100 nm. The rod has a diameter of 2-4 nm. Close to the middle of the rod there may be a flexible joint. The molecules appear to be attached to microtubules most often by their forked ends in the presence of AMP.PNP. However, the large branched end can also attach to microtubules and individual molecules occasionally have been seen cross-linking two microtubules.