Isolation of α and β brain tubulin subunits after alkaline treatment of the protein

We demonstrate here that brain purified tubulin can be dissociated into α and β subunits at pH > 10 and that the subunits can be separated by using the Triton X-114 phase separation system. After phase partition at pH > 10, α tubulin but not β tubulin behaves as a hydrophobic compound appearing in the detergent rich phase. After three extractions of the alkaline aqueous phase with Triton X-114, about 90% of the α tubulin was recovered in the detergent rich phase. The hydrophobic behavior observed for α tubulin after its dissociation at pH 11.5 was not due to an irreversible change of the protein, because when the detergent rich phase containing α tubulin was diluted with a buffer solution at pH 7.3 and the solution allowed to partition again, α-tubulin is recovered in the aqueous phase. The detergent in the aqueous phase of the α and β tubulin preparations can be removed up to 90% by 12 h dialysis. The α and β subunits of tubulin from kidney and liver behave, in this phase separation system, like those of brain tubulin.