Water-oxidizing complex

Huang, R Kurz, R Styring, S. 2007. EPR investigations of synthetic manganese complexes as bio-mimics of the water oxidation complex in photosystem II. Appl. Magn. Reson. 31 301-320. 

In photosynthesis, water oxidation is accomplished by photosystem II (PSII), which is a large membrane-bound protein complex (158-161). To the central core proteins D1 and D2 are attached different cofactors, including a redox-active tyro-syl residue, tyrosine Z (Yz) (158-162), which is associated with a tetranuclear manganese complex (163). These components constitute the water oxidizing complex (WOC), the site in which the oxidation of water to molecular oxygen occurs (159, 160, 164). The organization is schematically shown in Fig. 18. 

Dasgupta J, Ananyev G, Dismukes GC. Photoassembly of the water-oxidizing complex in photosystem II. Coord Chem Rev 2008 252 347-60. 

Han G, Li J, Chen G, et al. Reconstruction of the water-oxidizing complex in manganese-depleted Photosystem II using synthetic manganese complexes. J Photochem Photobiol B Biol 2005 81 114-20. 

Zaharieva I, Najafpour MM, Wiechen M, Haumann M, Kurz P, Dau H. Synthetic manganese-calcium oxides mimic the water-oxidizing complex of photosynthesis functionally and structurally. Energy Environ Sci. 2011 4(7) 2400-8. 

Carrel, T.G., Tyryshkin, A.M., and Dismukes, G.C. (2002) An evaluation of structural models for the photosynthetic water-oxidizing complex derived from spectroscopic and X-ray diffraction signatures, J. Biol. Inorg. Chem., 7, 2-22. 

Evance, M.C.W., Rich, A.M., and Nugent, J.H.A. (2000) Evidence for the presence of a component of the Mn complex of the Photosystem II reaction center which is exposed to water in the S2 state of the water oxidation complex, FEBS Letters, All, 113-117. 

Noguchi, T. and Sugiura, M. (2000) Structure of an Active Water Molecule in the Water-Oxidizing Complex ofPhotosystem II As Studied by FTIR Spectroscopy, Biochemistry 39, 10943-10949. 

Advances in the study of photosynthetic manganese and the water oxidation complex have been accelerated by the development of techniques for the isolation of photosystem II particles by Triton-X and/or digitonin treatment of thylakoid membranes (188,189). Freeze-fracture electron microscopy indicates the particles are highly purified membrane fragments almost entirely devoid of photosystem I components (190). The lumenal side of the photosystem II membrane is exposed, allowing direct access to the water oxidation enzyme complex. These PSII preparations contain four atoms of manganese per PSII reaction center and possess large amounts of 02 activity (191, 192). 

PSII = Photosystem II WOC = Water-oxidizing complex OEC = Oxygen-evolving complex (B)RC = (Bacterial) Reaction Center Chi = Chlorophyll Bchl = Bacteriochloro-phyll XRD = X-ray diffraction EPR = Electron paramagnetic resonance EXAFS = Extended X-ray absorption fine stmctnre ENDOR = Electron-nuclear double resonance ESEEM = Electron spin echo envelope modulation (Tyr = Yz) = DlTyrl61 ATP = Adenosine Triphosphate KIE = Kinetic isotope effect UV = Ultraviolet (FT-)IR = (Fourier Transform) InfraRed. 

Figure 2 XRD model of the cofactors bound to photosystem II RC core and the water-oxidizing complex. The view is perpendicular to the membrane normal. (Reprinted with permission from K. Ferreira, T. Iverson, K. Maghlaoui, J. Barber and S. Iwata, Science Express, DOI 1093087 (2004). 2004 AAAS)...

R13 Dismukes, G.C. (1986) The organization and function of manganese in the water-oxidizing complex of photosynthesis. In Manganese in Metabolism and Enzyme Function (Wedler, F.C. and Schram, V.L., eds.), Academic Press, New York, in the press. 

Sauer K, Yachandra VK. The water-oxidation complex in photosynthesis. Biochim. Biophys. Acta 2004 1655 140-148. 

K Sauer, VKYachandra, RD Britt and MP Klein (1992) The photosynthetic water oxidation complex studied by ERR and x-ray absorption spectroscopy. In VL Pecararo (ed) Manganese Redox Enzymes, pp 141-175. 

Fig. 7. (A) The oxidation states of Mn in the various S-states. The model incorporates a histidine radical formation in the Sj-state with no oxidation of Mn in the Sj- Sa transition the model also accommodates the 1 0 1 2 proton-release pattern in the Kok cycle (B) a proposed topological model for the photosynthetic water-oxidizing Mn-complex based on XAS and EPR studies. Figure source (A) [adapted] and (B) Sauer, Yachandra, Britt and Klein (1992) The photosynthetic water oxidation complex studied by EPR and X-ray absorption spectroscopy. In VL Pecararo (ed) Manganese Redox Enzymes, pp 141-175. VCH Publ.

S Padhye, T Kambara, DN Hendrickson and Govindjee (1986) Manganese-histidine clusters as the functional center of the water oxidation complex in photosynthesis. Photosynthesis Res 9 103-112RD... 

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