An international group has demonstrated that differential labeling of microtubules with glutamic acid chains acts as a "signpost" for directing MT-based trafficking within the cell. Different polyglutamylases preferentially target specific microtubule-based cellular structures such as cilia, and apparently regulate the movement of motor proteins along the MT's.

News release, NSF Website: http://www.nsf.gov/news/news_summ.jsp?cntn_id=104178