In vitro investigation of the photoprotection mechanism of Light Harvesting Complex II

Solar energy is used by\nphotosynthetic organisms to drive energy required cellular processes. Is\nabsorbed by two groups of pigments, located in the LHCs. These proteins are\nessential for the performance of photosynthesis, because they are involved in\nharvesting the light and because they\nprotect the photosynthetic system from excess of light that cause photodamage.\nI performed in vitro studies mimicking the two functions of LHCII by inserting\nthe protein in nanodiscs and in liposomes. I demonstrate that Chl excitation\nquenching is dependent on protein-protein interactions.\nI investigated the specific interactions of LHCII with PsbS. The fluorescence\nstudy of our minimal membrane models strongly suggests that the pH-dependent\nrole of PsbS lies in creating membrane rearrangements and supercomplex\nremodeling that could facilitate LHCII aggregation quenching.\nI successfully produced 13C lutein-rLhcb1 protein in detergent, mimicking the\nunquenched state, and protein aggregates, mimicking the quenched state, were\nbiochemically and spectroscopically characterized and further analysed with\nsolid state NMR.Ring current shifts of the lutein head signals indicate that\nthe heads are in close proximity to specific Chls (Chl a610 and Chl a602),\nproviding for the first-time structural information about lutein-Chl\ninteractions in LHCII in its unquenched state.