Anti-Polyglutamate chain [Poly-E]

Tubulin polyglutamylation stimulates spastin-mediated microtubule severing. Microtubules are key elements of the eukaryotic cytoskeleton that dynamically assemble from heterodimers of alpha- and beta-tubulin. Two different mechanisms can generate microtubule diversity: the expression of different alpha- and beta-tubulin genes, referred to as tubulin isotypes, and the generation of posttranslational modifications (PTMs) on alpha- and beta-tubulin. Tubulin PTMs include the well-known acetylation or phosphorylation, and others that have so far mostly been found on tubulin, detyrosination/tyrosination, polyglutamylation and polyglycylation. These PTMs might have evolved to specifically regulate tubulin and microtubule functions. Polyglutamylation is a PTM that occurs when secondary glutamate side chains are formed on gamma-carboxyl groups of glutamate residues in a protein. Enzymes catalyzing polyglutamylation belong to the TTL-like (TTLL, Tubulin tyrosine ligase-like) family of glutamylases. Deglutamylases, the enzymes that reverse polyglutamylation, were identified within a novel family of CCPs (cytosolic carboxypeptidase). Subtle differences in polyglutamylation can be seen on diverse microtubules in different cell types. The functions of these modifications remain to be studied. However, its wide distribution strengthens the idea that it could be involved in fine-tuning a range of microtubule functions.