X-ray structural analysis of S100 proteins.

X-ray crystallography is a potent and meanwhile fast technique to obtain detailed structural information of S100 proteins in their apo or metal ion-loaded state. S100 proteins crystallize in the absence or presence of Ca(2+) and Zn(2+) and the obtained crystals often diffract to high resolution yielding information on the ion-binding sites, conformation, and target interaction sites of the proteins. Here, I describe a general scheme to isolate and crystallize S100 proteins and the analysis of protein crystals using a modern synchrotron source.