Polymerization and colchicine binding. Two independent properties of tubulin.

When stored frozen in 1 M sucrose and 1 mM GTP, tubulin loses polymerizing ability exponentially. Since addition of diethiothreitol does not change the decay half-life, this decrease in activity can not be attributed to disulfide bond formation. When tubulin is stored frozen in dithiothreitol and GTP only, the decay half-life increases by a factor of four, indicating that sucrose destabilizes polymerizing ability. Frozen storage in sucrose has the opposite effect on colchicine binding, which remains at 100% for 40 days. This temporal divergence indicates that colchine binding and polymerization are two independent properties of tubulin.