(588h) Control of Insertion and Directionality of Synechocystis PCC. 6803 Photosystem I in in Vitro Liposomes

Samantha Clark¹, Guru Venkatesan², Andy Sarles², and Paul Frymier¹

¹Department of Chemical and Biomolecular Engineering, University of Tennessee Knoxville, 419 Dougherty Engineering Building, Knoxville, TN 37996; sclark40@utk.edu, pdf@utk.edu

²Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee Knoxville, 414 Dougherty Engineering Building, Knoxville, TN 37996; gvenkate@utk.edu, ssarles@utk.edu

Cell structure is maintained through complex interactions of phospholipids and proteins to form cell membranes. The membranes act as protective barriers against toxins and give functionality and stability to proteins embedded in the phospholipid bilayer. In cyanobacteria and green plants, photosynthetic complexes are amongst the proteins in the thylakoid membrane. These complexes are responsible for converting photons into usable energy. Photosystem I (PSI), part of this pathway, transfers electrons across the thylakoid membrane to form NADPH. Currently, PSI is predominantly studied in vitro while solubilized in detergent.  Recent work in our lab has shown that the detergents used to solubilize membrane proteins has a significant effect on protein structure and dyanamics.  A system where lipids provide the protection for the hydrophobic transmembrane domains is more appropriate for comparison to the natural system for PSI.  In the current study, we are interested in examining the effects of membrane constituents on protein-lipid structure and dynamics.  In this presentation, we examine the use of lipid vesicles to effectively simulate in vivo conditions for PSI.   In particular, we are interested in how the lipid constituents affect the directionality of insertion of the protein within the lipid vesicle wall.