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Uphill energy transfer mechanism for photosynthesis in an Antarctic alga.

Makiko KosugiMasato KawasakiYutaka ShibataKojiro HaraShinichi TakaichiToshio MoriyaNaruhiko AdachiYasuhiro KameiYasuhiro KashinoSakae KudohHiroyuki KoikeToshiya Senda
Published in: Nature communications (2023)
Prasiola crispa, an aerial green alga, forms layered colonies under the severe terrestrial conditions of Antarctica. Since only far-red light is available at a deep layer of the colony, P. crispa has evolved a molecular system for photosystem II (PSII) excitation using far-red light with uphill energy transfer. However, the molecular basis underlying this system remains elusive. Here, we purified a light-harvesting chlorophyll (Chl)-binding protein complex from P. crispa (Pc-frLHC) that excites PSII with far-red light and revealed its ring-shaped structure with undecameric 11-fold symmetry at 3.13 Å resolution. The primary structure suggests that Pc-frLHC evolved from LHCI rather than LHCII. The circular arrangement of the Pc-frLHC subunits is unique among eukaryote LHCs and forms unprecedented Chl pentamers at every subunit‒subunit interface near the excitation energy exit sites. The Chl pentamers probably contribute to far-red light absorption. Pc-frLHC's unique Chl arrangement likely promotes PSII excitation with entropy-driven uphill excitation energy transfer.
Keyphrases
  • energy transfer
  • quantum dots
  • binding protein
  • early onset
  • single cell
  • single molecule
  • reduced graphene oxide