Electrochemical and DNA-Binding Studies of a Modified Blue Copper Protein.
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It is conceivable that eukaryotes posses DNA proof-reading proteins that sense the difference in conductivity of perfectly matched DNA versus mismatched DNA. We are using stellacyanin, a small mononuclear blue copper protein of unknown biological function, to investigate this hypothesis. This protein contains a copper binding domain at the N-terminus, which creates a noticeable blue color upon the addition of copper. Stellacyanin is ideal for electrochemical studies as it forms films on electrodes without mediators, and because the copper binding domain is located near the N-terminus so it can be easily mutated. In addition, we have added amino acids to this protein allowing it to intercalate into DNA which has been tethered to a gold electrode surface. The ability of this engineered protein to bind to A-T rich oligonucleotides will be probed using DNA mobility shift studies. If DNA binding occurs then it may be possible to reduce the copper center by sending an electron through the double helix of DNA that is tethered to the gold surface. An efficient expression system for the wild type stellacyanin has been developed, enabling us to create stellacyanin mutants for further electrochemical experiments.