Journal Article

Structure of photosystem II and substrate binding at room temperature

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

2016

نظرة عامة

The structures of three intermediate states of photosystem II, which is crucial for photosynthesis, have been solved at room temperature, shedding new light on this process. Room temperature structures of photosystem II During the conversion of light into energy in plants, photosystem II oxidizes water within a Mn 4 CaO 5 cluster in the oxygen evolving complex (OEC). This process involves five intermediate states that have eluded structural determination until now. Junko Yano and colleagues use a femtosecond X-ray free electron laser (XFEL) to capture three of these states at room temperature. As the structure was solved in the presence of ammonia, a water analogue, the authors are able to conclude that the ammonia-binding Mn site is not a substrate water site. 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 ) 1 , 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 2 , 3 . 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 4 , 5 , 6 . 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 7 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 8 , 9 , 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 10 . Since the ammonia-bound OEC is active, the ammonia-binding Mn site is not a substrate water site 10 , 11 , 12 , 13 . This approach, together with a comparison of the native dark and 2F states, is used to discriminate between proposed O–O bond formation mechanisms.

• الناشر: Nature Publishing Group UK,Nature Publishing Group
• موضوع: 631/449/1734/2076 / 631/45/56 / 631/535/1266/1265 / 631/57/1464 / Ammonia - chemistry / Ammonia - metabolism / Bacterial Proteins - chemistry / Bacterial Proteins - metabolism / BASIC BIOLOGICAL SCIENCES / Binding Sites / Crystallization / Cyanobacteria - chemistry / Electrons / Humanities and Social Sciences / Lasers / letter / Manganese - metabolism / Models, Molecular / multidisciplinary / Oxygen - metabolism / Photosystem II / Photosystem II Protein Complex - chemistry / Photosystem II Protein Complex - metabolism / Physiological aspects / Science / Structure / Substrate Specificity / Substrates (Biochemistry) / Temperature / Water - metabolism