ABSTRACT
Photosystem I (PSI) and photosystem II (PSII) are the key proteins of the light reactions of oxygenic photosynthesis. They are universally distributed throughout prokaryotes and eukaryotes capable of oxygenic photosynthesis. They are present in green (higher) plants, macroalgae, diatoms, dinoflagellates, and the oxyphotobacteria (cyanobacteria and prochlorophytes), but not in archaea. Among these organisms, the core complexes of PSI and PSII are relatively well preserved compared to the peripheral antenna. In this chapter, we address the topic of how PSI and PSII are structurally organized in oxygenic photosynthesis. Covered are several examples of the large associations and focus on the variation in the membrane-bound peripheral antenna. Some other aspects, such as the spatial separation of PSI and PSII in the photosynthetic (thylakoid) membrane and the way the thylakoid membranes are spatially organized, are not discussed in detail. The structural aspects of two supercomplexes, involved in electron flow regulation, are also discussed.
