With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Steven O. Mansoorabadi from Auburn University, whose research project is focused on mechanistic and biosynthetic studies of dinoflagellate bioluminescence. Dinoflagellates are an important group of microorganisms found in freshwater and marine environments. Certain dinoflagellates produce potent toxins and cause red tides, which have a significant negative impact on coastal ecosystems and the health of humans and marine wildlife. Several species of dinoflagellates are both photosynthetic and bioluminescent, and are responsible for the bright blue glow of the sea. Dinoflagellates produce light in response to physical agitation using an enzyme known as dinoflagellate luciferase. The substrate of this enzyme, luciferin, is produced from chlorophyll by an unknown pathway. This research project aims to provide a better understanding of the dinoflagellate bioluminescence system by elucidating the mechanism of light production by dinoflagellate luciferase and the biosynthetic pathway for the production of luciferin. These studies help facilitate the use of dinoflagellate luciferase as a cellular imaging agent, and may lead to the development of algicides for the remediation of coastal seawater. This project also integrates bioluminescence, an exciting and fascinating natural phenomenon, into two K-12 outreach initiatives designed to attract and inspire young students to pursue careers in science and related fields. It will also include students in the Auburn University Summer Science Institute directed at gifted high school students and the AU Explore a program that engages middle school students from predominantly rural schools
Dinoflagellate luciferase is a model system for the study of both pH-dependent enzyme regulation and the chemical mechanism of biological chemiluminescence, neither of which are well understood. To gain insight into the regulation of dinoflagellate luciferase, the magnitude and timescale of the pH-induced conformational change and the associated variations in structure and dynamics is determined using time-resolved photothermal methods, constant pH molecular dynamics simulations, and hydrogen/deuterium exchange mass spectrometry. The detailed mechanism by which dinoflagellate luciferase produces light is investigated by determining the structure of the luminophore and other key catalytic intermediates using a combination of transient kinetic and spectroscopic methods and time-dependent density functional theory calculations. In addition, the identity of active site residues important for substrate binding and catalysis is ascertained using mutational analysis. Finally, insight into the pathway of chlorophyll catabolism leading to the formation of dinoflagellate luciferin is obtained through the biochemical and structural characterization of identified biosynthetic intermediates and enzymes. Together, these studies provide significant insight into the biochemistry of these important marine microorganisms and afford excellent interdisciplinary training opportunities for undergraduate and graduate students.
