Modulating Copper Enzymatic Activity by Tuning Secondary Coordination Sphere Interactions

With support from the Chemistry of Life Processes Program in the Chemistry Division, Dr. Yi Lu at the University of Texas at Austin is studying how copper (Cu) enzymes play vital roles in nature, driving important chemical reactions. Their activities are driven by two main factors: the Cu-binding primary coordination sphere (PCS) and the non-binding secondary coordination sphere (SCS) around PCS.

The SCS effects are not well understood due to the weak, non-covalent interactions within the complex protein environment. While studying native copper enzymes has provided valuable information, it is difficult to draw general conclusions across different classes of proteins from this approach. This project uses simplified model proteins to study how the SCS affects Cu enzymes in processes such as breaking down plant biomass and transferring nitric oxide (NO), a molecule that performs important signaling functions in humans and other animals.

The findings could enhance our fundamental knowledge of metal biochemistry and could lead to practical applications in biocatalysis in sustainable energy and artificial NO storage and transportation systems. Additionally, this research will support the Chemical Biology program in the Department of Chemistry at the University of Texas at Austin. Latest research results will be incorporated into educational programs for high school and undergraduate students from diverse backgrounds.

This project employs a novel biosynthetic approach to impart new or improved activity at protein Cu centers, aided by unnatural amino acids and loop-directed mutagenesis to deconvolute factors controlling activity. The research could advance fundamental knowledge of the roles of the SCS in controlling Cu enzymatic activity by obtaining a holistic understanding of how this environment can modulate the reactivity of copper enzymes, including 1) tuning the reduction potentials of the T1Cu center in small laccase to modulate its activity towards the oxygen reduction reaction in fuel cells and lignin degradation, 2) controlling polysaccharide degradation activity by a designed Cu-histidine-brace center in azurin, mimicking lytic polysaccharide monooxygenase, and 3) regulating reversibility of S-nitrosylation and trans-nitrosylation between the enzymes and small molecules in azurin.

By imparting new activity on a scaffold lacking SCS as in native enzymes, the knowledge gained from the proposal may be transformative not only within the Cu enzyme chemistry, but more broadly beyond bioinorganic chemistry, because most systems require fine-tuning of the SCS environment to achieve efficient catalysis.

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.