Bpb, NEF, Protein S100-A1, S100 beta, S100 calcium binding protein A1, S100A, S100B, 100beta,
Weakly binds calcium but binds zinc very tightly-distinct binding sites with different affinities exist for both ions on each monomer. Physiological concentrations of potassium ion antagonize the binding of both divalent cations, especially affecting high-affinity calcium-binding sites.