Each of us is part metal. Our bodies contain iron, copper, zinc, magnesium, manganese, vanadium, molybdenum, selenium, and even nickel like the coins in our pockets or purses. Unlike the other common elements of life (carbon, oxygen, hydrogen, calcium, nitrogen, phosphorus), our metals are not synthesized and recycled, but must be imported and handled with care. Copper is a good example of a biological metal that performs multiple useful functions – that is, unless something goes wrong with the machinery handling it.
Richard A. Festa and Dennis J. Thiele (Duke University of Medicine) began an article in Current Biology explaining why biological metals are fascinating:1
Life on Earth has evolved within a complex mixture of organic and inorganic compounds. While organic molecules such as amino acids, carbohydrates and nucleotides form the backbone of proteins and genetic material, these fundamental components of macromolecules are enzymatically synthesized and ultimately degraded. Inorganic elements, such as copper (Cu), iron and zinc, once solubilized from the Earth’s crust, are neither created nor destroyed and therefore their homeostatic regulation is under strict control. In the fascinating field of ‘metals in biology’, by virtue of direct interactions with amino acid side-chains within polypeptide chains, metals play unique and critical roles in biology, promoting structures and chemistries that would not otherwise be available to proteins alone.
Because copper can exist in an reduced state (Cu+) and an oxidized state (Cu2+), it is a candidate for versatile functions – as indeed it is employed in all living things. But copper is also a potential toxin: “free intracellular Cu can generate hydroxyl radicals, which can damage proteins, nucleic acids, and lipids, and can interfere with the synthesis of iron–sulfur clusters that are essential for the activity of a number of important cellular enzymes.” It must, therefore, be handled with care. Here is a short list of machines that handle this useful but risky metal:….
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