Antibodies to synthetic peptides from the tubulin regulatory domain interact with tubulin and microtubules.

The carboxyl-terminal region of tubulin alpha and beta subunits plays a major role in regulating its assembly into microtubules and constitutes an essential domain for the selective interaction of microtubule-associated proteins (MAPs). With the goal of understanding the structural basis of the regulatory function of the carboxyl-terminal domains of tubulin subunits, we have produced rabbit antisera against two MAP-interacting peptides Lys-Asp-Tyr-Glu-Glu-Val-Gly-Val-Asp-Ser-Val-Glu of alpha-tubulin and Tyr-Gln-Gln-Tyr-Gln-Asp-Ala-Thr-Ala-Asp-Glu-Gln-Gly of beta subunit. The affinity-purified alpha and beta anti-peptide antibodies interacted specifically with tubulin and with the respective peptide antigens but did not interact with MAPs. Substoichiometric amounts of both antibodies showed the capacity to inhibit in vitro MAP-induced tubulin assembly and to promote a fast depolymerization of preassembled microtubules. Taxol-promoted assembly of pure tubulin was not inhibited by the antibodies. In the presence of MAP-2 and taxol, the antibodies decreased the MAP-2 content of taxol-promoted microtubules. The interaction with microtubules was corroborated by immunofluorescence experiments in HeLa and NE-18 lung carcinoma cells. The epitopes recognized by the alpha and beta anti-peptide antibodies appear to be located in the outer surface of the microtubular structure.