A standard procedure in pufying tubulin is to extract the tissue on ice, then add GTP and warm the tissue extract to 37C. The warmed extract is then centrifuged at a speed insufficient to pellet average sized proteins, but sufficient to pellet large protein complexes. After centrifugation, the supernant is discarded, and the solution is agian warmed for a few minutes. Then centrifugation at the same speed described above is again performed. This process is repeated several times.
How would this processs result in purification of tubulin?
What contaminating proteins would likely co-purify with the tubulin?