Binding of transition metals to SIO0 proteins

The S100 proteins are a unique class of EF-hand Ca2＋ binding proteins distributed in a cell-specific, tissue-specific, and cell cycle-specific manner in humans and other vertebrates. These proteins are distinguished by their distinctive homodimeric structure, both intracellular and extracellular functions, and the ability to bind transition metals at the dimer interface. Here we summarize current knowledge of S 100 protein binding of Zn2＋, Cu2＋ and Mn2＋ ions, focusing on binding affinities, conforma- tional changes that arise from metal binding, and the roles of transition metal binding in S 100 protein function.