Studying Drug-Tubulin Interactions by X-Ray Crystallography

Tubulin, the microtubule building-block, is the target of numerous small molecule compounds that interfere with microtubule dynamics. Several of these ligands are in clinical use as antitumor drugs. There have been numerous studies on these molecules, with two main objectives: to determine their mechanism of action and to find new compounds that would expand the arsenal available for cancer chemotherapy. Although these studies would undoubtedly benefit from structural data on tubulin, this protein has long resisted crystallization attempts. We have used stathmin-like domains (SLDs) of stathmin family proteins as a tool to crystallize tubulin and have obtained three-dimensional crystals of the tubulin:SLD complexes. As many tubulin ligands bind to these complexes, the crystals are valuable tools to study tubulin-drug interactions by X-ray crystallography. They open the way to a structure-based drug design approach.