CAREER: Probing Structure and Expanding Function with Genetically Encoded Non- Canonical Amino Acids

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Twenty amino acids naturally occur in living systems where they serve as building blocks of proteins. These proteins, in turn, have key functions in cells. With this award, the Chemistry of Life Processes Program in the Chemistry Division is funding Dr. Christine Phillips-Piro from Franklin and Marshall College to use non-canonical amino acids (ncAAs), i.e., amino acids that do not occur in living systems, to investigate the structure and to systematically modify the function of proteins. The addition of new ncAAs results in unusual proteins that have very different functions than those made with the natural amino acids. The research project provides interdisciplinary training for undergraduate researchers in chemistry, molecular biology, biochemistry, and protein structure determination. Dr. Phillips-Piro's courses enable undergraduate students to learns about current scientific research. She integrates scientific literacy in two different courses - general chemistry and a general education course. Her team also helps to organize and run a regional chemistry conference for undergraduates (the Intercollegiate Student Chemists? Convention (ISCC)). Professor Phillips-Piro is a member of the Advanced Photon Source User Organization (APSUO) which seeks to broaden participation at Argonne National Laboratory. The research supported by this award exploits a targeted collection of ncAAs being used to both study protein structure and tune protein function. Local environments in a thermostable heme nitric oxide and/or oxygen binding protein (H-NOX) are assessed by using the ncAA vibrational reporter 4-cyano-L-phenylalanine in concert with temperature-dependent infrared spectroscopy and X-ray crystallography. The systematic modulation of the the oxygen binding affinity of the heme protein is achieved by using tyrosine ncAAs with altered phenolic hydrogen acidity. These moieties influence the strength of hydrogen bonding between a key amino acid residue (Y140) distal to the heme and the small molecule bound to the heme. Metal-binding ncAAs are used to generate a novel bimetallic enzyme based on the H-NOX scaffold. The insights gained and tools developed by Dr. Phillips-Piro may benefit other scientists who employ ncAAs to probe, modify, and/or engineer biological systems.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.