The association of carbohydrate with tubulin and in vitro assembled microtubules from bovine brain.

Phosphocellulose-purified tubulin (PC tubulin) was analyzed for neutral and amino sugar content, which was found to be 8.3 +/- 0.11 and 0.8 +/- 0.02 mol/mol dimer, respectively. A histochemical-electron-microscopic investigation was undertaken to attempt to localize carbohydrate associated with polymerized microtubules (MT). Outer diameters of MT assembled in vitro from bovine brain MT protein (tubulin and microtubule associated proteins) were found to increase upon treatment with ruthenium red, Alcian blue, and lanthanum hydroxide, which have been reported to possess specificity for complex carbohydrates. Concanavalin A-reactive sites were detected on the surface and in the lumen of MT assembled from MT protein and from PC tubulin.