Metal-Ion Binding

TLDR: This chapter describes metal–ion binding, a type of binding in which metal binds reversibly to specific amino acid residues in the polypeptide chain but is not required for biological activity and indeed may even impair protein function or disrupt protein structure.

Abstract: Publisher Summary This chapter describes metal–ion binding. Two general classes of proteins are considered for describing metal–ion binding. These are (1) systems in which the metal ion occupies a small number of very high energy sites and is essential for the biological function of the macromolecule (e.g., alkaline phosphatase, carboxypeptidase) and (2) systems in which metal binds reversibly to specific amino acid residues in the polypeptide chain but is not required for biological activity and indeed may even impair protein function or disrupt protein structure. Metal ions, like protons, share electron pairs from the donor atoms of a ligand molecule and, thus, form partially covalent bonds with characteristic heats of formation. This type of binding is distinguished from binding to proteins of neutral molecules or large organic ions such as detergents, where the large binding forces are primarily entropie in origin. All metal ions have sets of characteristic coordination numbers that represent the number of hybrid bonds available for ligands. The binding of metal ions to proteins can be measured by equilibrium dialysis.