The tubulin code is a traffic controller

Microtubules are cylindrical polymers constructed from the protein tubulin that serve as a highway for vesicle and organelle transport.

Tubulin is one of the most extensively covalently modified proteins known. The compendium of modifications [including acetylation, glutamylation, glycylation, nitrosylation, palmitoylation, phosphorylation, polyamination (spermine, spermidine), sumoylation and de/retyrosination] is termed the Tubulin Code.

Interestingly, tubulin’s carboxy-terminal tail, which protrudes from the surface of the microtubule is a hot-spot for covalent modification.

Deciphering the functional significance of the code has been hampered by problems in expressing recombinant tubulin and the mixed composition (re: modifications and isotypes) of tubulin prepared from brain. Ron Vale’s group (Howard Hughes Med. Inst., University of California, San Francisco) successfully engineered and expressed chimaeras between the core of yeast tubulin and the carboxy-terminal tails of human tubulin, thereby allowing the role a single modification to be investigated.

The researchers demonstrate that the presence or absence of polyglutamate and tyrosine within the tail affects the motility of microtubular motors kinesin and dynein. Hence, the tubulin code is a traffic controller.