Palladium(II) and Platinum(II) Bind Strongly to an Engineered Blue Copper Protein

Studies of palladium­(II) and platinum­(II) binding to well-characterized proteins contribute to understanding the influence of these metals in the environment and body. The well-characterized apoprotein of azurin has a soft-metal binding site that may be exposed to solvent by mutation of a coordinating His-117 residue to glycine (H117G). Palladium­(II) and platinum­(II) form strong 1:1 adducts with the apo form of H117G azurin. A combination of UV–vis, circular dichroism, and inductively coupled plasma mass spectrometry techniques suggests that the metal binds specifically at His-46 and Cys-112 of the protein.