Abstract
Colchicine-binding properties of the total cytoplasmic pool of tubulin from rat liver were evaluated in tubulin-stabilizing (TS) supernates. Microtubules were separated from free tubulin using a microtubule-stabilizing solution (MTS) and ultracentrifugation. [3H]Colchicine-binding properties of microtubule-derived tubulin were investigated in supernates prepared after resuspension of MTS pellets in TS. In TS buffer at 37 °C the colchicine-binding activity of the total cytoplasmic pool of tubulin decayed with T1/2 of 3.39 h. Resuspended pellet tubulin decayed much more rapidly under the same conditions with a T1/2 of 0.72 h. This rapid time decay of microtubule-derived tubulin was found to be at least partially attributable to prior microtubule-stabilizing solution exposure. Since tartrate has been reported to increase the rate of colchicine binding to tubulin, sodium tartrate (150 mm) was added to our colchicine-binding system. This addition increased the detectable [3H]colchicine binding by 10% in the total cytoplasmic preparation and by 85% in the resuspended pellet preparation. Addition of tartrate (150 mm) also resulted in a 105% increase in the T1/2 for total cytoplasmic tubulin and a 412% increase for microtubule derived tubulin. Total cytoplasmic supernates of liver bound [3H]colchicine linearly over a wide range of tissue concentrations. However, resuspended microtubule-stabilizing solution pellet supernates in tubulin-stabilizing solution showed some increase in colchicine binding per tissue weight in the more dilute samples. Our data which demonstrate differences in colchicine-binding properties for total cytoplasmic and microtubule-derived pools of tubulin suggest that present assays for hepatic tubulin polymerization which assume identical binding properties should be interpreted with caution.
Original language | English (US) |
---|---|
Pages (from-to) | 181-190 |
Number of pages | 10 |
Journal | Archives of Biochemistry and Biophysics |
Volume | 204 |
Issue number | 1 |
DOIs | |
State | Published - 1980 |
ASJC Scopus subject areas
- Biophysics
- Biochemistry
- Molecular Biology