Effects of Metal Binding on Protein Structure

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Abstract
A distinction has been made between ‘metalloproteins’ and ‘metal-protein complexes’. The former exhibit high metal-ligand stability constants (the metal is not removed during the isolation of the protein), while the latter bind metal ions only loosely (Vallee, 1955). Actually, all proteins can be considered as existing as metal-protein complexes. Selectivity, however, among proteins in their tendency to combine with inorganic ions (both with regard to the type of ion as well as number of ions) suggests that particular configurations produce specific reactive sites. In turn, binding of ions to these sites alters the electronic and consequently the steric conformation of the protein. Thus, effects on macromolecular conformation may not only be due to structural changes of the solvent induced by ions, which modifies solvent-macromole interaction, but also to specific ligation of the ions to the protien which alters local molecular arrangement.