CAREER: Unraveling Diverse Mechanisms of Heme Degradation Processes

Saint Louis University, Saint Louis MO

Investigators

Abstract

This award is funded in part under the American Rescue Plan Act of 2021 (Public Law 117-2). With the support of the Chemistry of Life Processes Program in the Division of Chemistry, Piotr Mak from Saint Louis University will study fundamental principles that govern the reactivity of heme iron-dependent enzymes, that play crucial roles in living systems and also have potential industrial applications. The proposed activities will have a significant societal impact on understanding human physiology as well as environmentally safe biotechnological processes. It is expected that the proposed combination of powerful research tools will provide vital information regarding the structure and function of heme proteins that is otherwise unlikely to be revealed. Another important aspect of the proposed work is to actively involve graduate and undergraduate students in multi-disciplinary research projects that will provide them with a wide range of exciting training opportunities. Additionally, the proposed outreach efforts will improve inclusion of underrepresented groups in STEM (Science, Technology, Engineering and Mathematics) fields by developing and implementing a program called “Seeing the Invisible”, which will enable high school students from socioeconomically disadvantaged communities to participate in the process of scientific discovery. Heme oxygenases, besides their role in heme catabolism, have many other important physiological functions in eukaryotes and pathogens. Heme degradation is a complex, multi-step process and despite many years of study, significant questions remain regarding the nature of the reactive intermediates involved in the catalytic activity of canonical heme oxygenases. Additionally, some recently discovered noncanonical enzymes catalyze a new type of heme degradation chemistry, leading to entirely different metabolites which imply new and unique reaction pathways. While it is of great importance to elucidate factors that dictate reactivity patterns of these proteins, such as the nature and structural dynamics of their reactive intermediates, progress has been thwarted by the extremely rapid decay of these unstable species for reactions conducted in solution. This application proposes that the combination of resonance Raman spectroscopy with cryo-radiolysis and nanodisc sampling methodology will allow for generation, stabilization, and characterization of these elusive species under conditions that mimic their natural environment. This unique approach has the potential to provide information regarding structure-function relationships in heme proteins that would be inaccessible by alternate methods. The significance of these studies lies in their contribution to the understanding of oxygen activation chemistry, which is an essential function of a wide array of dioxygen-utilizing heme enzymes and various other metalloproteins. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.