Characterization of Metal Proteins

Abstract

Some metals are essential for life. Most of these metals are associated with biological macromolecule like DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and more often with proteins: metals bind or interact with them. A number of protein molecules intrinsically contain metals in their structure. Some of these proteins catalyze unique chemical reactions and perform specific physiological functions. In this chapter, we will shed light on the several metal-containing proteins, termed metalloproteins, and other proteins interacting metals. We will also introduce several key techniques which have been used to characterize these proteins. Characterizing these proteins and to understand the relationships between their structures and functions shall continue to be one of the major avenues to solve the mysteries of life. At first, we introduce what are the protein structures and how these proteins interact with metals. In the next section, we discuss the physiological roles of some representative metals. Next, we show two examples of special metal cofactors those help the biological macromolecules to carry out their functions. Then we describe some functions of metalloproteins. Finally, we introduce some physical methods to characterize metalloproteins. 9.2 Proteins and Metals A protein molecule is made from a long chain of amino acids, each linked to its neighbor through a covalent peptide bond. Each of proteins has its own particular amino acid sequence, and each of the 20 different amino acids has unique side chains with distinctive properties. Some of these side chains are nonpolar and hydrophobic, others are negatively or positively charged, some are reactive, and so on. These side chains limit greatly possible bond angles in a polypeptide chain. This constraint and other steric interactions severely