Structure of tubulin rings studied by X-ray scattering using synchrotron radiation.

X-ray patterns have been obtained from solutions of microtubules and tubulin rings using synchrotron radiation. They are interpreted on the basis of the oriented fiber X-ray diagram of microtubules, and by comparing them with the calculated scattering traces of model structures. The data are consistent with models in which rings consist of coiled protofilaments. This is in agreement with some published ring models while it excludes others.