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De novo design of proteins housing excitonically coupled chlorophyll special pairs.

Nathan M EnnistShunzhi WangMadison A KennedyMariano CurtiGeorge A SutherlandCvetelin VasilevRachel L RedlerValentin MaffeisSaeed ShareefAnthony V SicaAsh Sueh HuaArundhati P DeshmukhAdam P MoyerDerrick R HicksAvi Z SwartzRalph A CachoNathan NovyAsim K BeraAlex KangBanumathi SankaranMatthew P JohnsonAmala PhadkuleMike ReppertDamian C EkiertGira BhabhaLance J StewartJustin R CaramBarry L StoddardElisabet RomeroChristopher Neil HunterJulien S Baker
Published in: Nature chemical biology (2024)
Natural photosystems couple light harvesting to charge separation using a 'special pair' of chlorophyll molecules that accepts excitation energy from the antenna and initiates an electron-transfer cascade. To investigate the photophysics of special pairs independently of the complexities of native photosynthetic proteins, and as a first step toward creating synthetic photosystems for new energy conversion technologies, we designed C 2 -symmetric proteins that hold two chlorophyll molecules in closely juxtaposed arrangements. X-ray crystallography confirmed that one designed protein binds two chlorophylls in the same orientation as native special pairs, whereas a second designed protein positions them in a previously unseen geometry. Spectroscopy revealed that the chlorophylls are excitonically coupled, and fluorescence lifetime imaging demonstrated energy transfer. The cryo-electron microscopy structure of a designed 24-chlorophyll octahedral nanocage with a special pair on each edge closely matched the design model. The results suggest that the de novo design of artificial photosynthetic systems is within reach of current computational methods.
Keyphrases
  • energy transfer
  • electron microscopy
  • high resolution
  • quantum dots
  • electron transfer
  • single cell
  • single molecule
  • computed tomography
  • small molecule