Fluorine, chlorine, bromine, and iodine are highly reactive elements called halogens. Attaching halogens to other molecules (halogenation) is an important chemical reaction. However, attaching halogens to a specific atom chemically is difficult, imprecise, and often exhibits low yields. With the support from the Cellular and Biochemistry Engineering (CBE) Program in the Division of Chemical, Bioengineering, Environmental and Transport Systems (CBET) and the Chemistry of Life Processes (CLP) Program in the Division of Chemistry (CHE), this project represents an attempt to overcome these problems using enzymes designed to add halogens to molecules. An enzyme that naturally adds chlorine and bromine to molecules with high specificity will be redesigned to add fluorine as well. The scientific communication skills of students and post docs engaged in the project will be strengthened through coaching and instruction. The participation of underrepresented minority students will be designed to stimulate their scientific curiosity.

SyrB2 is a non-heme iron halogenase that catalyzes chemo- and regio-selective chlorination/bromination of amino acid threonine using environmentally-friendly oxygen, alpha-ketoglutarate, and chloride/bromide as starting materials. Its reaction scope and substrate promiscuity will be broadened by rationally modulating the enzyme’s primary and secondary coordination sphere as well as protein-protein interactions. Objective 1 focuses on developing ligand activators that expand the reaction scope to include fluorination. Objective 2 designs hydrogen-bond interactions to a halohydroxoferric intermediate that expands its substrate promiscuity to other amino acids. Objective 3 engineers decoy peptides that eliminate the dependency of SyrB2 on its protein partner for delivering the substrate and triggering catalysis. The project will advance structural, functional, and mechanistic knowledge of non-heme iron enzymes and establish the framework for the rational and computational design of iron-dependent enzymes for sustainable synthetic chemical processes.

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.

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University of Minnesota Twin Cities
United States
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