Photosynthesis is the primary solar energy transformation process that powers life on Earth1. In order to efficiently capture solar radiation, diverse photosynthetic apparatuses have evolved in different types of photosynthetic organisms. Two photosystems work together in tandem in higher plants, whereas in cyanobacteria there are supramolecular mega-complexes found4. Anoxygenic photosynthetic prokaryotes are diverse groups of bacteria thriving worldwide since the early history of the planet. In most species of photosynthetic prokaryotes, light energy is initially absorbed by the peripheral light-harvesting (LH) antenna and then transferred via the inner LH to the reaction center (RC), where the primary reaction of photosynthesis occurs. The primary separated electron is transferred within the RC to a quinone. The fully reduced quinol is then exchanged with an oxidized quinone from the membrane pool and passes its electrons to the next redox component in the cyclic electron transfer pathway, during which a transmembrane proton gradient is established for the subsequent production of ATP. In purple bacteria, the core RC–LH1 and the peripheral LH2 were found and they share a similar modular architecture. The basic unit of both LHs is an αβ-heterodimer, which binds BChl a and carotenoid as light-harvesting pigments. In the near-infrared region, the LH2 complex has two absorption bands around 800 and 850 nm, whereas the core RC–LH1 complex has a single strong peak at 880 nm. In contrast to LH2, where highly resolved X-ray structures are available, diverse structural characteristics of the RC–LH1 core complex were discovered, which are related to how quinol is released from the RC, passes through the palisade of the LH antenna and is exchanged with quinone from the membrane pool. Here you can see a cryo-EM structure of native RC-LH complex from Roseiflexus castenholzii (PDB code: 8J5P)

#molecularart ... #immolecular ... #photosynthesis ... #complex ... #membrane ... #bacteria ... #cryoem

Structure rendered with @proteinimaging and depicted with @corelphotopaint