Mammalian brain tubulin consists of several isotypes of α and β subunits that separate on polyacrylamide gels into three electrophoretic classes, designated α, β1, and β2. It has not been possible hitherto to resolve the different isotypes in a functional form. To this end, we have now isolated a monoclonal antibody, using as an immunogen a chemically synthesized peptide corresponding to the carboxyl-terminal sequence of the major tubulin isotype (type II) found in the β1-tubulin electrophoretic fraction. The antibody binds to β1 but not to α or β2. When pure tubulin from bovine brain is passed through an immunoaffinity column made from the anti-type II antibody, the tubulin that elutes in the unbound fraction is enriched greatly for the β2 electrophoretic variant. The tubulin that binds to the column appears to contain only α and β1, not β2. When these tubulin fractions are characterized by immunoblotting using the anti-type II antibody, the antibody binds only to the β1 band in the bound fraction, not to the β1 band in the unbound fraction. Using polyclonal antibodies generated against the carboxyl-termini of types I, III, and IV, we demonstrate that the β1 electrophoretic species is comprised of isotypes I, II, and IV, whereas the β2 variant is comprised exclusively of type III β-tubulin. Further, we calculate that β-tubulin in purified bovine brain tubulin is comprised of 3% type I, 58% type II, 25% type III, and 13% type IV tubulins.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|State||Published - 1988|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology