Brain and erythrocyte microtubules from chicken contain different beta-tubulin polypeptides.

beta-Tubulin subunits isolated from chicken brain tissue and erythrocytes are distinguishable as unique biochemical species by electrophoretic and peptide mapping procedures. 1) The subunits of beta-tubulin exhibit major differences in electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels that vary according to the pH and ionic strength of the gel. 2) The isoelectric points of urea-denatured beta subunits from brain tissue and erythrocytes are pH 5.1 and 5.4, respectively, whereas those of both alpha subunits are approximately pH 5.2.3) Two-dimensional peptide maps prepared with alpha-chymotrypsin or V8 protease show that alpha-tubulin peptides are indistinguishable, whereas beta-tubulin peptides are very different. Only one-third of the 15 major tyrosine-containing beta-tubulin peptides prepared with alpha-chymotrypsin are common to both beta-tubulin species. The data indicate that the beta-tubulin subunits of brain tissue and erythrocytes are biochemically distinct and may be different gene products. The presence of tubulin variants in brain tissue and erythrocytes may indicate special requirements for microtubule assembly and function in different cell types.