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Open Access Publications from the University of California

Structure of photosystem II and substrate binding at room temperature.

  • Author(s): Young, Iris D
  • Ibrahim, Mohamed
  • Chatterjee, Ruchira
  • Gul, Sheraz
  • Fuller, Franklin
  • Koroidov, Sergey
  • Brewster, Aaron S
  • Tran, Rosalie
  • Alonso-Mori, Roberto
  • Kroll, Thomas
  • Michels-Clark, Tara
  • Laksmono, Hartawan
  • Sierra, Raymond G
  • Stan, Claudiu A
  • Hussein, Rana
  • Zhang, Miao
  • Douthit, Lacey
  • Kubin, Markus
  • de Lichtenberg, Casper
  • Long Vo, Pham
  • Nilsson, Håkan
  • Cheah, Mun Hon
  • Shevela, Dmitriy
  • Saracini, Claudio
  • Bean, Mackenzie A
  • Seuffert, Ina
  • Sokaras, Dimosthenis
  • Weng, Tsu-Chien
  • Pastor, Ernest
  • Weninger, Clemens
  • Fransson, Thomas
  • Lassalle, Louise
  • Bräuer, Philipp
  • Aller, Pierre
  • Docker, Peter T
  • Andi, Babak
  • Orville, Allen M
  • Glownia, James M
  • Nelson, Silke
  • Sikorski, Marcin
  • Zhu, Diling
  • Hunter, Mark S
  • Lane, Thomas J
  • Aquila, Andy
  • Koglin, Jason E
  • Robinson, Joseph
  • Liang, Mengning
  • Boutet, Sébastien
  • Lyubimov, Artem Y
  • Uervirojnangkoorn, Monarin
  • Moriarty, Nigel W
  • Liebschner, Dorothee
  • Afonine, Pavel V
  • Waterman, David G
  • Evans, Gwyndaf
  • Wernet, Philippe
  • Dobbek, Holger
  • Weis, William I
  • Brunger, Axel T
  • Zwart, Petrus H
  • Adams, Paul D
  • Zouni, Athina
  • Messinger, Johannes
  • Bergmann, Uwe
  • Sauter, Nicholas K
  • Kern, Jan
  • Yachandra, Vittal K
  • Yano, Junko
  • et al.

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Light-induced oxidation of water by photosystem II (PS II) in plants, algae and cyanobacteria has generated most of the dioxygen in the atmosphere. PS II, a membrane-bound multi-subunit pigment protein complex, couples the one-electron photochemistry at the reaction centre with the four-electron redox chemistry of water oxidation at the Mn4CaO5 cluster in the oxygen-evolving complex (OEC). Under illumination, the OEC cycles through five intermediate S-states (S0 to S4), in which S1 is the dark-stable state and S3 is the last semi-stable state before O-O bond formation and O2 evolution. A detailed understanding of the O-O bond formation mechanism remains a challenge, and will require elucidation of both the structures of the OEC in the different S-states and the binding of the two substrate waters to the catalytic site. Here we report the use of femtosecond pulses from an X-ray free electron laser (XFEL) to obtain damage-free, room temperature structures of dark-adapted (S1), two-flash illuminated (2F; S3-enriched), and ammonia-bound two-flash illuminated (2F-NH3; S3-enriched) PS II. Although the recent 1.95 Å resolution structure of PS II at cryogenic temperature using an XFEL provided a damage-free view of the S1 state, measurements at room temperature are required to study the structural landscape of proteins under functional conditions, and also for in situ advancement of the S-states. To investigate the water-binding site(s), ammonia, a water analogue, has been used as a marker, as it binds to the Mn4CaO5 cluster in the S2 and S3 states. Since the ammonia-bound OEC is active, the ammonia-binding Mn site is not a substrate water site. This approach, together with a comparison of the native dark and 2F states, is used to discriminate between proposed O-O bond formation mechanisms.

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