Biomimetic Aspects of Copper Binding in Copper-Peptide Complexes

Kentucky State University, Frankfort KY

Investigators

Abstract

The study of metalloprotein active sites through the investigation of model complexes provides useful insights on protein function in relation to physical structure and chemical environment. The role of biomimetic approaches is considered essential for understanding the factors that influence reactivity at the metal-centered active sites of metalloproteins. Studies on the active site of oxyhemocyanin are incomplete since most of the model complexes prepared to date are unstable at room temperature and are incompatible with water. This project involves the design, preparation, structural characterization and dioxygen reactivity of the copper binding domain in copper-peptide complexes that have room temperature stability and the potential to serve as models, in aqueous media, for the metal binding site of oxyhemocyanin. A two-fold synthetic approach to producing appropriate peptide ligands for the models will be employed: (a) use of peptides that are conformationally organized by copper to place two copper binding domains in close proximity; (b) use of peptides that constrain copper at a predetermined distance within a disulfide link. Copper-peptide complexes will be prepared with ligands produced under these approaches. They will be examined for (i) copper binding stoichiometry, (ii) the conditions for copper coordination exclusively through the imidazole side chain of histidine and (iii) the presence of a turn conformation that places copper ions in close proximity. Subsequent to establishing the targeted copper binding characteristics, the copper-peptide complexes will be examined for reactivity with dioxygen to produce copper-dioxygen adducts and for their ability to incorporate dioxygen with a binding motif that is a replica of copper binding site in oxyhemocyanin. The research will also investigate isolating the copper-dioxygen adducts as a larger unit attached to a streptavidin-biotin complex. The results from these studies will provide foundation for developing a broad and long-range research program. Broader Impacts: Kentucky State University is a minority serving institution. The activities of the project will build the research capacity at Kentucky State University by providing a viable and sustained project through which underrepresented minority students will receive research training. Students will perform research both at Kentucky State University and within the research-rich environment at Texas A&M University. The knowledge and experienced gained in implementing the project will be used to advance the educational objectives of the Division of Mathematics and Sciences through the development of new courses and diversification of course offerings.