Purification, crystallization and preliminary X-ray diffraction studies on human Ca2+-binding protein S100B.

S100B, a Ca2+-binding protein, acts intracellularly as a Ca2+-signalling protein but is also secreted to the extracellular space, acting in a cytokine-like manner through its receptor RAGE. Recombinant human S100B has been purified and crystallized in the Ca2+-bound state. Size-exclusion chromatography indicates that S100B can exist as a dimer and as a multimer in solution. Crystals of S100B diffract to 1.9 A and belong to space group P2(1), with unit-cell parameters a = 63.4, b = 81.6, c = 71.5 A, alpha = 90, beta = 107, gamma = 90 degrees. Preliminary analysis of the X-ray data indicate that there are four homodimers per asymmetric unit.