Session: Undergraduate Research Posters: Biochemistry:

Photosynthesis is a crucial process in biological organisms' activities which converts light energy into chemical energy, and the process is powered by a series of electron transfers. Plastocyanin is a blue copper protein with four amino acids bound to the copper center, called the inner shell. It transports electrons between cytochrome f and photosystem I, where light energy is used to produce ATP and NADPH.
The coordination of the inner shell residues gives unique properties to the redox activity of plastocyanin, making it an efficient electron shuttle. We aim to figure out what role the outer shell residues, which are away from the copper center and do not directly bind it, will have in tuning the activity of plastocyanin. Our hypothesis is that modifying outer shell residues will impact the plastocyanin copper center through removal of hydrogen bonding interactions. Using site-directed mutagenesis, four outer shell residues were mutated to alanine, and the impact of those mutations were observed through Infrared Spectroscopy. The analysis was performed through use of a deuterated amino acid probe replacing one inner shell residue to give a well characterized signal. Through collecting the FTIR spectra on the mutant and wild type plastocyanin samples, and each in complex with binding partner cytochrome f, we can observe changes impacted by mutations. We also plan to perform redox titrations of each mutant to determine impacts on the redox potential.
Through this work, we can have a better view of characterization of plastocyanin, and how it plays a key role in shuffling electrons. The result can be used for further understanding of electron transfer in photosynthesis, which provides an important source of energy.

Megan Thielges

Indiana University

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