Abstract
Tubulin, the dimeric structural protein of microtubules, is a heterodimer of α and β subunits; both α and β exist as numerous isotypes encoded by different genes. In vertebrates the sequence differences among the βI, βII, βIII, βIV and βV isotypes are highly conserved in evolution, implying that the isotypes may have functional significance. Isotype-specific monoclonal antibodies have been useful in determining the cellular and sub-cellular distributions and possible functions of the βI; βII, βIII, and βIV isotypes; however, little is known about the βV isotype. We here report the creation and purification of a monoclonal antibody (SHM.12G11) specific for βV. The antibody was designed to be specific for the C-terminal sequence EEEINE, which is unique to rodent and chicken βV. The antibody was found to bind specifically to the C-terminal peptide EEEINE, and does not cross-react with the carboxy-termini of either α-tubulin or the other β-tubulin isotypes. However, the antibody also binds to the peptide EEEVNE, but not to the peptide EEEIDG, corresponding respectively to the C-terminal peptides of bovine and human βV. Immunofluorescence analysis indicates that βV is found in microtubules of both the interphase network and the mitotic spindle. In gerbils, βV also occurs in the cochlea where it is found largely in the specialized cells that are unique in containing bundled microtubules with 15 protofilaments.