Stabilization of microtubule protein in glycerol solutions

The consequences of short-term storage of microtubule protein at 0 °C have been examined and the ability of glycerol to prevent loss of activity has been evaluated. Three forms of activity monitored include colchicine-binding activity, critical concentration, and relative polymerizing activity. Colchicine-binding activity decayed continuously and glycerol increased the half-life roughly in proportion to its concentration (t1/2 = 57 days in 4 M glycerol). Critical concentration remained relatively constant for 2–3 days and then increased rapidly in the absence of glycerol. This rapid increase was delayed in glycerol concentrations above 1 M. Relative polymerizing activity was based in this work on the slope of the critical concentration plot. In most cases, loss of activity was apparent after as little as 24 h. This was the first observed alteration in polymerization properties of the microtubule protein and glycerol concentrations below 3 M had little effect in slowing the decay. Degradation of microtubule-associated proteins may account for these changes in polymerization properties that occurred more rapidly than tubulin denaturation. Evidence for degradation was demonstrated by sodium dodecyl sulfate gel electrophoresis. Higher glycerol concentrations slowed this degradation.