Ph.D. Student Purdue University West Lafayette, Indiana
Body of Abstract: The photosynthetic electron transport chain harbors several protein-pigment complexes necessary for converting light energy into usable forms of chemical energy. Photosystem II (PSII) harnesses the nearly inexhaustible energy of light to split abundant water into oxygen and protons. Although this reaction is necessary for oxygenic photosynthesis, highly intense light conditions often result in generation of reactive oxygen species (ROS) that subsequently damage amino acids of PSII. To limit the photoinhibitory effects of oxidative damage to PSII, the D1 subunit of PSII is rapidly and selectively degraded allowing for de novo synthesis and replacement of a new D1. The thylakoid membrane-embedded PSII-LHCII supercomplex therefore requires a stepwise lateral disassembly allowing for the access of D1 by proteolytic machinery. Although this process is known to occur quite rapidly, it is still unclear how the D1 subunit is accessed and selectively degraded from this massive protein complex. Post-translational modifications including phosphorylation and oxidative damage are thought to assist in the rapid disassembly of PSII, however, their exact role is still unknown. We have therefore utilized several biochemical techniques to characterize the roles of PTMs on the assembly status of the PSII complex. We have demonstrated that phosphorylation assists in the disassembly of PSII supercomplexes, while oxidative protein damage induces detachment of the CP43 subunit from dimeric and monomeric PSII. The results of this work will be useful for understanding the life-cycle of one of the most abundant membrane proteins in the world.