Microtubules are involved in a wide variety of intracellular events including cell division, intracellular transport and secretion, axonal transport, and maintenance of cell morphology. They are composed of tubulin, a heterodimeric protein, consisting of two polypeptides, α-tubulin and β-tubulin (1).
α Tubulin undergoes numerous post-translational modifications that include tyrosination-detyrosination and deglutamylation, phosphorylation, acetylation, polyglutamylation, and polyglycylation. In one of the major posttranslational modifications, the C-terminal tyrosine residue in α-tubulin is added or removed reversibly, producing Glu-tubulin (after detyrosination) and Tyr-tubulin (with re-added tyrosine). Early stages of cell development are often enriched in Tyr tubulin, whereas mature cells show increased Glu tubulin in stable structures. Some microtubule associated proteins (MAPs), motor proteins like kinesins, or stabilizing factors have different affinities for Glu- or Tyr-tubulin (2,3,4).
A third variant of detyrosinated α-tubulin is Δ2-tubulin which lacks the C-terminal glutamic acid. It cannot be tyrosinated by tyrosine ligase and is one of the dominant α-tubulin isoforms in neurons (5).