LAUSR

Enzymes that detyrosinate the microtubule cytoskeleton are identified Microtubules are cytoskeletal filaments that drive chromosome segregation during cell division, control cell shape and motility, and serve as rails for motor protein-based intracellular transport. Microtubules are polymers built of highly conserved subunits, α- and β-tubulin, which contain a globular core and more variable C-terminal tails that are exposed at the microtubule surface. Although microtubules are structurally uniform, they display functional specialization due to the combination of different tubulin isoforms and multiple posttranslational modifications (1). Many of these modifications occur within the C-terminal tails and affect microtubule interactions with motor proteins or regulatory factors. The first tubulin modifications were discovered more than 40 years ago and consist of the catalytic removal and reincorporation of the C-terminal tyrosine, an amino acid residue that is present in most α-tubulin isotypes (see the figure) (2–4). Whereas retyrosination of soluble tubulin is known to be mediated by tubulin-tyrosine ligase (5), α-tubulin detyrosination, which occurs preferentially on microtubules, is mediated by an unknown carboxypeptidase activity. On pages 1448 and 1453 of this issue, Aillaud et al. (6) and Nieuwenhuis et al. (7) report the identification and characterization of vasohibins as long-sought tubulin carboxypeptidases.