Metal-free MIRAS phasing: structure of apo-S100A3

Metal-free S100A3, a cysteine-rich Ca²⁺- and Zn²⁺-binding protein, has been crystallized by vapour diffusion under the strict exclusion of oxygen and in the absence of divalent metal ions. The structure was solved by MIRAS phasing using potassium iodide and xenon derivatives.