The long range goal of this project is to study structure-function relationships in cytochromes P450 and related proteins using x-ray crystallography, molecular biology, and biochemistry. This competitive renewal focuses on the following areas: a newly discovered P450 called P450cin that has the unusual property of using an FMN-containing protein as the electron donor; oxy-complexes of various P450s and mutants; conformational dynamics in P450BM3 and; heme oxygenase. These various projects address the structure of important intermediates in the catalytic cycle for both P450 and heme oxygenase. Redox complexes will be studied using kinetics and crystallography, in addition to NMR spectroscopy using the new 800MHz instrument recently installed at UCI.