A broad description of the work being performed in this laboratory would include the mechanisms of metalloproteins involved in radical generation, heme synthesis, as well as the mechanisms of heme sensing, aquisition and transport. With very few exceptions, heme is required by most organisms for a vast array of heme dependent enzymes and biosensors. More recently, a number of heme regulated pathways have been identified that have a far reaching impact on human health. Areas of focus range from heme aquisition and sensing by both bacterial (pathogenic) and human systems to the heme regulated activities of cytochrome P450s involved in cholesterol biosynthesis and the degradation of chemotherapeutic compounds in humans. We are also interested in the atomic details of radical generation and transfer in the family of glycyl radical containing enzymes. These enzymes are activated by an activating enzyme that utilizes a [4Fe-4S] cluster to catalyze the reductive cleavage of S-adenosylmethionine (SAM). Similar to heme function, these enzymes are widespread in Nature and serve to catalyze a number of difficult and essential reactions. Of particular interest is the mechanism by which a radical SAM enzyme "activates" another enzyme through protein-protein interactions and transfer of a highly reactive radical.