X-ray kinetic studies of microtubule assembly using synchrotron radiation.

The assembly of microtubules has been investigated by time-resolved X-ray diffraction using synchrotron radiation. The small-angle scattering becomes visible within seconds and thus enables study of the structural transitions of the protein aggregates during assembly from their subunits in solution. The X-ray pattern at 4 degrees C arises from a mixture of tubulin rings, dimers and some other species. Raising the temperature to 36 degrees C induces the breakdown of rings, followed by the growth of microtubules. The results suggest that microtubules may be formed from tubulin oligomers smaller than rings.