Subsets of microtubules enriched in posttranslationally detyrosinated (Gundersen, G. G., M. H. Kalnoski, and J. C. Bulinski. 1984. Cell. 38:779) or acetylated (Piperno, G., M. Le Dizet, and X. Chang. 1987. J. Cell Biol. 104:298), alpha tubulin have previously been described in interphase cultured cells. In this study an immunofluorescence comparison of these minor populations of microtubules revealed that, in African green monkey kidney epithelial cells (TC-7 line), the population of microtubules enriched in detyrosinated tubulin was virtually coincident with the population enriched in acetylated alpha tubulin. In some cell types, however, such as human HeLa or marsupial PtK-2 cells, only one posttranslationally modified form of tubulin, i.e., acetylated or detyrosinated, respectively, was detectable in microtubules. In TC-7 cells, although both modifications were present, dissimilar patterns and kinetics of reappearance of microtubules enriched in detyrosinated and acetylated tubulin were observed after recovery of cells from microtubule-depolymerizing treatments or from mitosis. Thus, a minor population of microtubules exists in cultured cells that contains an elevated level of tubulin modified in either one or two ways. While these two modifications occur primarily on the same subset of microtubules, they differ in their patterns of formation in vivo.

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