CAREER: The Interaction of Nitric Oxide with Cytochrome P450

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This CAREER award in the Inorganic, Bioinorganic and Organometallic Chemistry program and the Molecular and Cellular Biology program supports work by Professor Nicolai Lehnert at the University of Michigan to probe the interaction of nitric oxide (NO) with cytochrome P450. The goal of this project is to obtain fundamental insight into the spectrum of redox transformations of NO that can be catalyzed by cytochrome P450s. The investigations utilize both the enzyme cytochrome P450cam and synthetic model complexes. Magnetic circular dichroism and resonance Raman spectroscopy are used to establish the relative donor strengths of the thiolate ligands in different model complexes and P450cam wild type and mutants. Ferrous and ferric heme nitrosyls are prepared and their spectroscopic properties, electronic structures, and reactivities are studied as a function of the thiolate donor strength. Biologically relevant reactions of these nitrosyl complexes are then investigated, including in particular the reduction of NO to N2O as mediated by P450nor (NO detoxification) and the reaction of ferrous heme nitrosyls with O2 and superoxide (nitrosative stress). A new undergraduate course on the role of metals in life is being developed to attract underrepresented minority students to the basic sciences. The class focuses on the relation between fundamental biological and chemical processes and questions of high current impact in society like health, the environment and alternative energy sources. Follow-up programs for hands-on research experiences in these areas are designed for these students. Nitric oxide is a double-edged sword in biological systems: it is of central importance for many signaling and regulating processes, but at too high concentrations it also constitutes a deadly threat to the organism. The clarification of the fundamental reactions between cytochrome P450s and NO is of key importance for biological chemists to determine how P450s could participate in the biological network of NO signaling, transformation and detoxification. In particular, it is expected that the reactions between NO and cytochrome P450s identified in the research could potentially be relevant to human physiology.