Details

Autor(en) / Beteiligte

• Kern, Jan
• Chatterjee, Ruchira
• Young, Iris D
• Fuller, Franklin D
• Lassalle, Louise
• Ibrahim, Mohamed
• Gul, Sheraz
• Fransson, Thomas
• Brewster, Aaron S
• Alonso-Mori, Roberto
• Hussein, Rana
• Zhang, Miao
• Douthit, Lacey
• de Lichtenberg, Casper
• Cheah, Mun Hon
• Shevela, Dmitry
• Wersig, Julia
• Seuffert, Ina
• Sokaras, Dimosthenis
• Pastor, Ernest
• Weninger, Clemens
• Kroll, Thomas
• Sierra, Raymond G
• Aller, Pierre
• Butryn, Agata
• Orville, Allen M
• Liang, Mengning
• Batyuk, Alexander
• Koglin, Jason E
• Carbajo, Sergio
• Boutet, Sébastien
• Moriarty, Nigel W
• Holton, James M
• Dobbek, Holger
• Adams, Paul D
• Bergmann, Uwe
• Sauter, Nicholas K
• Zouni, Athina
• Messinger, Johannes
• Yano, Junko
• Yachandra, Vittal K

Titel

Structures of the intermediates of Kok's photosynthetic water oxidation clock

Ist Teil von

• Nature (London), 2018-11, Vol.563 (7731), p.421-425

Ort / Verlag

England: Nature Publishing Group

Erscheinungsjahr

2018

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• Inspired by the period-four oscillation in flash-induced oxygen evolution of photosystem II discovered by Joliot in 1969, Kok performed additional experiments and proposed a five-state kinetic model for photosynthetic oxygen evolution, known as Kok's S-state clock or cycle . The model comprises four (meta)stable intermediates (S , S , S and S ) and one transient S state, which precedes dioxygen formation occurring in a concerted reaction from two water-derived oxygens bound at an oxo-bridged tetra manganese calcium (Mn CaO ) cluster in the oxygen-evolving complex . This reaction is coupled to the two-step reduction and protonation of the mobile plastoquinone Q at the acceptor side of PSII. Here, using serial femtosecond X-ray crystallography and simultaneous X-ray emission spectroscopy with multi-flash visible laser excitation at room temperature, we visualize all (meta)stable states of Kok's cycle as high-resolution structures (2.04-2.08 Å). In addition, we report structures of two transient states at 150 and 400 µs, revealing notable structural changes including the binding of one additional 'water', Ox, during the S →S state transition. Our results suggest that one water ligand to calcium (W3) is directly involved in substrate delivery. The binding of the additional oxygen Ox in the S state between Ca and Mn1 supports O-O bond formation mechanisms involving O5 as one substrate, where Ox is either the other substrate oxygen or is perfectly positioned to refill the O5 position during O release. Thus, our results exclude peroxo-bond formation in the S state, and the nucleophilic attack of W3 onto W2 is unlikely.