Structure of photosystem II and substrate binding at room temperature
Journal article
Publication Details
Author list: Young I.D., Ibrahim M., Chatterjee R., Gul S., Fuller F.D., Koroidov S., Brewster A.S., Tran R., Alonso-Mori R., Kroll T., Michels-Clark T., Laksmono H., Sierra R.G., Stan C.A., Hussein R., Zhang M., Douthit L., Kubin M., De Lichtenberg C., Vo Pham L., Nilsson H., Cheah M.H., Shevela D., Saracini C., Bean M.A., Seuffert I., Sokaras D., Weng T.C., Pastor E., Weninger C., Fransson T., Lassalle L., Bräuer P., Aller P., Docker P.T., Andi B., Orville A.M., Glownia J.M., Nelson S., Sikorski M., Zhu D., Hunter M.S., Lane T.J., Aquila A., Koglin J.E., Robinson J., Liang M., Boutet S., Lyubimov A.Y., Uervirojnangkoorn M., Moriarty N.W., Liebschner D., Afonine P.V., Waterman D.G., Evans G., Wernet P., Dobbek H., Weis W.I., Brunger A.T., Zwart P.H., Adams P.D., Zouni A., Messinger J., Bergmann U., Sauter N.K., Kern J., Yachandra V.K., Yano J.
Publication year: 2016
Volume number: 540
Issue number: 7633
Pages: 453-457
Publisher: Nature Publishing Group
URL: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84994458775&origin=inward
Languages: English-Great Britain
Abstract
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 Mn 4 CaO 5 cluster in the oxygen-evolving complex (OEC). Under illumination, the OEC cycles through five intermediate S-states (S 0 to S 4), in which S 1 is the dark-stable state and S 3 is the last semi-stable state before O-O bond formation and O 2 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 (S 1), two-flash illuminated (2F; S 3 -enriched), and ammonia-bound two-flash illuminated (2F-NH 3; S 3 -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 S 1 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 Mn 4 CaO 5 cluster in the S 2 and S 3 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.
