Biogenesis of thylakoid membranes in cyanobacteria

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The thylakoid membrane (TM) represents the site of the energy-producing photosynthetic electron transport via the protein/pigment complexes photosystem II (PSII), Cytb6f and photosystem I (PSI). While the structure and working mode of this molecular machine is well understood, less is known about its development during ontogenesis. This research project is dedicated to the elucidation of the spatial/temporal organization of TM biogenesis in the cyanobacterial model system Synechocystis sp. PCC 6803. As a case study, we will focus on the assembly of PSII, especially its oxygen-evolving manganese cluster, which we have recently been postulated to take place in specialized biogenesis centers close to the plasma membrane. In this regard, the periplasmic PratA factor as well as the gene product of reading frame slr0483 seem to play essential roles. While the tetratricopeptide repeat (TPR) protein PratA transports manganese and, thus, is directly involved in the maturation of the water splitting apparatus of PSII, the membrane protein Slr0483p appears to be generally required for the formation of biogenesis centers based on latest ultrastructural investigations.The goal of the planned work is to gain detailed insights into the molecular working mode as well as the spatial organization of these factors by applying molecular genetical, biochemical/biophysical and electron microscopical methods. In addition other factors like the recently identified PratA interaction partners, i.e., Slr1277p and the Deg-protease HhoA will be analyzed in regard to their function and subcellular localization. Parallel X-ray structure analysis of the PratA/D1 complex will reveal details of the manganese uptake process by the D1 protein of PSII. This work will be complemented by biochemical analyses of PratA-related factors from green algae and vascular plants to test for an evolutionary conserved manganese delivery to PSII.