who was kooper in the cell
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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 (Fe) and zinc (Zn), 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.
After the rise of photosynthetic organisms such as the cyanobacteria, oxygen accumulated in the atmosphere and oxygenated the oceans. This led to a decrease in the solubility of Fe and an expansion of the biological role of Cu, suggesting there was a shift from exclusively Fe in biology to embrace similar, though not identical roles for Cu. One property of Cu that drives its diverse roles in structure and catalysis, is its existence in either a reduced, Cu+, or oxidized, Cu2+, state. Since Cu+ has an affinity for thiol and thioether groups (examples found in cysteine or methionine), and Cu2+ exhibits preferred coordination to oxygen or imidazole nitrogen groups (found in aspartic and glutamic acid, or histidine, respectively), these metal ions can participate in a wide spectrum of interactions with proteins to drive diverse structures and biochemical reactions (Table 1). Moreover, in the process of moving between Cu+ and Cu2+, free intracellular Cu can generate hydroxyl radical, which can damage proteins, nucleic acids, and lipids, and can interfere with the synthesis of Fe-sulfur clusters that are essential for the activity of a number of important cellular enzymes. Additionally, the Irving-Williams series predicts that Cu can displace other metals such as Zn from their cognate ligands in metalloproteins, resulting in inappropriate protein structures or inhibition of enzymatic activity. Here we provide a brief overview of some roles for Cu in biology in bacterial, fungal, plant and mammalian systems, and we outline key ways that Nature balances the acquisition, distribution and regulation of Cu. It will become clear that as life evolved, more complex roles for Cu arose, concurrent with the elaboration of mechanisms to tightly regulate acquisition, distribution and the protection against Cu toxicity.
After the rise of photosynthetic organisms such as the cyanobacteria, oxygen accumulated in the atmosphere and oxygenated the oceans. This led to a decrease in the solubility of Fe and an expansion of the biological role of Cu, suggesting there was a shift from exclusively Fe in biology to embrace similar, though not identical roles for Cu. One property of Cu that drives its diverse roles in structure and catalysis, is its existence in either a reduced, Cu+, or oxidized, Cu2+, state. Since Cu+ has an affinity for thiol and thioether groups (examples found in cysteine or methionine), and Cu2+ exhibits preferred coordination to oxygen or imidazole nitrogen groups (found in aspartic and glutamic acid, or histidine, respectively), these metal ions can participate in a wide spectrum of interactions with proteins to drive diverse structures and biochemical reactions (Table 1). Moreover, in the process of moving between Cu+ and Cu2+, free intracellular Cu can generate hydroxyl radical, which can damage proteins, nucleic acids, and lipids, and can interfere with the synthesis of Fe-sulfur clusters that are essential for the activity of a number of important cellular enzymes. Additionally, the Irving-Williams series predicts that Cu can displace other metals such as Zn from their cognate ligands in metalloproteins, resulting in inappropriate protein structures or inhibition of enzymatic activity. Here we provide a brief overview of some roles for Cu in biology in bacterial, fungal, plant and mammalian systems, and we outline key ways that Nature balances the acquisition, distribution and regulation of Cu. It will become clear that as life evolved, more complex roles for Cu arose, concurrent with the elaboration of mechanisms to tightly regulate acquisition, distribution and the protection against Cu toxicity.
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