Most photosynthetic proteins are synthesized in the cytoplasm of the plant cell but are used in the thylakoid membrane of the chloroplast. The cpTAT pathway is a transport pathway in the thylakoid that helps move photosynthesis-related proteins to their site of function and requires the work of three membrane proteins, Tha4, Hcf106, and cpTatC. Membranes, like the thylakoid, are composed of lipids, and Tha4 must insert itself into the lipids of the thylakoid to do its job of helping other proteins get across the membrane. Tha4 undergoes conformational (shape) change when it inserts into the thylakoid membrane and disrupts the membrane locally. We seek to quantify this disruption by introducing Tha4 to lipid vesicles containing fluorescent dye and measuring the dye release upon protein interaction. Additionally, the extent of the conformational change Tha4 undergoes will be measured with a technique called circular dichroism spectroscopy. We expect maximal dye release in vesicles that most closely mirror thylakoid lipid bilayers, suggesting that the bilayer induces a conformational change in Tha4. More accurate models of the cpTAT pathway can be proposed if we learn more about Tha4 insertion activity, thus leading to higher understanding of protein transport.
Authors: Madelyn Smith and Eunice Nsaam
Faculty Advisor: Dr. Carole Dabney-Smith, Department of Chemistry and Biochemistry
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