Supporting data for “The Regulation of Tubulin Isotypes in Tubulin Tyrosination, Microtubule Stability and Polarized Growth"

Tubulin isotypes are critical for the functions of cellular microtubules, which exhibit different stability and harbour various post-translational modifications. However, how tubulin isotypes determine the activities of regulators for microtubule stability and modifications remains unknown. Here, we show that human α4A-tubulin, a conserved genetically detyrosinated α-tubulin isotype, is a poor substrate for enzymatic tyrosination. To examine the stability of microtubules reconstituted with defined tubulin compositions, we develop a strategy to site-specifically label recombinant human tubulin for single-molecule TIRF microscopy-based in vitro assays. The incorporation of α4A-tubulin into the microtubule lattice stabilizes the polymers from passive and MCAK-stimulated depolymerization. Further characterization reveals that tubulin isotypes not only regulate the microtubule dynamicity but also determine the microtubule polarized growth. In particular, the first minus-end preferential growth of microtubule is discovered in our study. It is determined that tubulin isotypes polymerize into microtubules with varying stability and polarity preferences. These insights into the functional role of tubulin isotypes have implications for understanding microtubule structure and polarity maintenance in cells.