The 4 angstrom X-ray structure of a tubulin : stathmin-like domain complex

Phosphoproteins of the stathmin family interact with the alpha beta tubulin heterodimer (tubulin) and hence interfere with microtubule dynamics. The s tructure of the complex of GDP-tubulin with the stathmin-like domain of the neural protein RB3 reveals a head-to-tail assembly of two tubulins with a 91-residue RB3 alpha helix in which each copy of an internal duplicated seq uence interacts with a different tubulin. As a result of the relative orien tations adopted by tubulins and by their alpha and beta subunits, the tubul in:RB3 complex forms a curved structure. The RB3 helix thus most likely pre vents incorporation of tubulin into microtubules by holding it in an assemb ly with a curvature very similar to that of the depolymerization products o f microtubules.