Mechanistic Investigation of Radical SAM Methylases Involved in Tetrahydromethanopterin Biosynthesis

With the support of the Chemistry of Life Processes Program in the Division of Chemistry, Dr. Kylie Allen from Virginia Tech and Dr. Evert Duin from Auburn University will study the mechanism of the enzyme known as MptM, a member of the radical S-adenosylmethionine (SAM) methylase family of enzymes, involved in tetrahydromethanopterin biosynthesis.

Tetrahydromethanopterin is a modified version of folate (vitamin B9) that is essential for methane production by microorganisms known as methanogens. This project aims to uncover the unique chemistry and the biological significance of MptM catalysis. In doing so, this research has the potential to provide foundational knowledge toward a better understanding of the formation of methane in the biosphere, with potential implications for bioenergy applications.

Students of various education levels will be directly engaged in this research, thus inspiring the next generation of scientists, and providing important interdisciplinary training opportunities. Several STEM(science, technology, engineering and mathematics) outreach activities will be expanded upon as a result of this funding, including hands-on workshops for elementary students and summer programs for middle and high school students.

This project has the potential to advance our knowledge of radical SAM enzyme mechanisms through biochemical and spectroscopic characterization of MptM- the founding member of the class D radical SAM methylases. Specifically, this research will identify the methyl group donor(s), determine the roles of three [4Fe-4S] clusters, and examine other key mechanistic aspects of the two MptM-catalyzed methylation reactions in tetrahydrobiopterin biosynthesis in methanogens.

Genetic studies will also be carried out to determine the in vivo functions and essentiality of two homologous radical SAM methylases in a model methanogen. Taken together, these projects will help to define the enzymatic mechanism and physiological functions of radical SAM methylases in methanogens, expanding the ever-increasing catalytic repertoire of radical SAM enzymes.

Related putative class D radical SAM methylases with currently unknown functions are found outside of methanogens; therefore, this work will aid in characterizing a broad group of enzymes likely involved in diverse natural product biosynthetic pathways.

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.