Browsing by Subject "Copper transport"

Copper was first released into the environment as the result of the mass generation of oxygen from photosynthetic bacteria roughly 2.7 billion years ago. While it proved to be poisonous to early life on Earth, those that met the evolutionary challenge utilized the metal as a cofactor in enzymes to perform biochemically significant functions, while controlling intracellular levels of copper with a sophisticated network of trafficking proteins. Proteins and enzymes that utilize copper as a cofactor have evolved significantly different coordination environments than copper trafficking proteins, as a result of the different functions they perform. Of particular interest was characterizing the unique Cu(I) binding events observed in some of these proteins, the extracellular N-terminal regions of eukaryotic high affinity copper transport proteins (Ctr), and the bacterial periplamsic CusF protein of the CusFBCA Cu(I)/Ag(I) efflux pathway.

Model peptides corresponding to the methionine rich binding motifs (Mets motifs) were characterized in terms of Cu(I) binding affinity, stoichiometry, and metal specificity, via an ascorbic acid oxidation assay and electrospray ionization mass spectrometry. Metal induced structural features and coordination environments were elucidated with NMR, CD and X-ray spectroscopy. A series of peptides was also examined to infer the relative Cu(I) binding affinities, and susceptibility to oxidation, of methionine, histidine, cysteine residues found in copper binding motifs. The resistance of Cu+ specific peptides to metal catalyzed oxidation is also described. Attempts were also made to model the Cu(I)/Ag(I) tryptophan cation-π interaction observed in CusF.

Mechanisms of copper homeostasis are of great interest partly due to their connection to debilitating genetic and neurological disorders. The family of high-affinity copper transporters (Ctr) is responsible for extracellular copper acquisition and internalization in yeast, plants, and mammals, including human. The extracellular domain of the human high-affinity copper transporter (hCtr1) contains essential Cu-binding methionine-rich MXXM and MXM (Mets) motifs that are important for copper acquisition and transport. The hCtr1 extracellular domain also contains potential copper binding histidine (His) clusters, including a high-affinity Cu(II) ATCUN site. As of yet, extracellular His clusters have no established significance for hCtr1 function. We have made model peptides based on the extracellular copper acquisition domain of hCtr1 that is rich in His residues and Mets motifs. The peptides' Cu(I) and Cu(II) binding properties have been characterized by UV-Vis and mass spectrometry. Our findings have been extended to a mouse cell model and we show that His residues are important for hCtr1 function likely because of their contribution to strong copper-binding sites in the hCtr1 extracellular domain responsible for copper acquisition.

Copper's pro-oxidant property is also medicinally promising if it can be harnessed to induce oxidative stress as a cancer chemotherapy strategy. Our lab has designed a photocleavable caged copper complex that can selectively release redox-active copper in response to light. The thermodynamic copper binding properties of these potential chemotherapeutics have been characterized