Steven Mansoorabadi, PhD, College of Sciences and Mathematics Faculty and Staff

Professional Experience

• Associate Professor, Auburn University, 2018-current
• Assistant Professor, Auburn University, 2012-2018
• Postdoctoral Associate, The University of Texas at Austin, 2006-2012
• Laboratory Technician, University of Wisconsin-Milwaukee, 1999-2000

Innovation

Our laboratory uses a combination of bioinformatic, biochemical and biophysical approaches to identify and characterize novel biosynthetic pathways, secondary metabolites and biocatalysts. The systems under study in our laboratory are chosen for both their biological importance and their potential for employing unusual and interesting enzyme chemistry.

Several research projects in our laboratory focus on tetrapyrrole biosynthesis. Tetrapyrroles, the “pigments of life,” are an important class of biomolecules that function as coenzymes and prosthetic groups. They play essential roles in fundamental biological processes, including oxygen and electron transport, photosynthesis, methanogenesis, nitrite and sulfite reduction, and fatty and nucleic acid metabolism.

Coenzyme F430

Coenzyme F430 is the nickel corphinoid prosthetic group of methyl-coenzyme M reductase, or MCR. MCR is the key enzyme in the biological formation of methane, a potent greenhouse gas and biofuel. MCR has also been shown to catalyze the anaerobic oxidation of methane.

In addition to housing coenzyme F430, the active site of MCR contains several unprecedented post-translational modifications, including 2-(S)-methylglutamine, 5-(S)-methylarginine, 3-methylhistidine, S-methylcysteine and thioglycine residues. The exact roles these post-translational modifications play in MCR catalysis are unknown, as are the identities of the genes responsible for biosynthesis of the unusual nickel-containing tetrapyrrole.

Identifying and characterizing the genes responsible for coenzyme F430 biosynthesis and MCR maturation may open new avenues in metabolic pathway engineering for the development of designer strains of methanogenic microorganisms for biofuel production. Detailed studies of the enzymes involved in these processes may also support the development of specific inhibitors to help reduce natural greenhouse gas emissions and shed light on novel mechanisms of proteome diversification in methanogenic archaea.

Dinoflagellate Luciferin

Dinoflagellates are an important group of eukaryotic microorganisms found in freshwater and marine environments. Certain taxa produce potent toxins, such as brevetoxin and saxitoxin, which cause neurotoxic and paralytic shellfish poisoning. Dinoflagellates are also responsible for red tides, the harmful algal blooms that can negatively affect coastal ecosystems and the health of humans and marine wildlife.

Several species of dinoflagellates are both photosynthetic and bioluminescent. The choice between photosynthesis and luminescence is regulated by a cellular circadian clock, with the phase set by light-dark cycles of day and night. A key event in this circadian regulation is the degradation of chlorophyll to the open-chain tetrapyrrole dinoflagellate luciferin, the light-emitting molecule used by the dinoflagellate luciferase enzyme.

The genes and enzymes responsible for the breakdown of chlorophyll to dinoflagellate luciferin are unknown, though the chemistry involved is likely to resemble chlorophyll catabolism in senescent leaves and ripening fruits of higher plants. Inhibition of this process results in the accumulation of chlorophyll catabolites that lead to light-induced cell death.

Identifying and characterizing the enzymes involved in dinoflagellate luciferin biosynthesis may lead to the development of specific pathway inhibitors with potential applications in the remediation of coastal seawaters. These studies may also help facilitate the use of dinoflagellate luciferase as a reporter enzyme and cellular imaging agent.