Thermodynamics of Metal-Protein Interactions

Dartmouth College, Hanover NH

Investigators

Abstract

With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Dean Wilcox from Dartmouth College as he seeks to obtain new insights into the binding of metal ions to proteins. Metals are often used in Nature due to the unique reactivity they provide when they are bound to a protein (e.g., metalloenzymes). Proteins play key roles in the uptake, transport, use and excretion of biologically essential metals (e.g., zinc, copper, iron), as well as toxic ones (e.g., mercury, lead, cadmium), by living organisms. Dr. Wilcox's studies are providing fundamental insights into how proteins interact with metal ions in the cell. Additionally, students working on this project are gaining important knowledge and valuable skills for their careers in science and education, thereby enhancing the scientific workforce. This research quantifies the thermodynamics of metal ions binding to proteins in order to provide a better understanding of metal contributions to protein stability and protein modulation of metal redox properties. Fundamental new insights about metal-protein interactions are being obtained from studies that correlate metal-binding thermodynamics to the thermodynamics of metal stabilization of the resulting metalloprotein. The Wilcox group quantifies solvent contributions to metal-binding thermodynamics, and determine metal contributions (bonding, electrostatics) to metalloproteins binding to DNA. A method that determines the metalloprotein reduction thermodynamics from calorimetric measurements of metal binding is being applied to selected metalloproteins and enzymes. These methods provide insight into protein modulation of the metal reduction potential, as well as proton transfer accompanying reduction. Several variants of azurin with higher and lower reduction potentials, polysaccharide monooxygenase, which has a unique Cu(I) coordination, and tyramine-monooxygenase, which has two mechanistically-distinct copper ions are being studied. Finally, this method is being extended to studies of the copper enzyme superoxide dismutase to quantify the thermodynamics and accompanying proton transfer reactions.