Photosystem II. structure

Vermaas W. Molecular-biological approaches to analyze photosystem II structure and function. Annu Rev Plant Physiol Plant Mol Biol 1993 44 457-481. 

Bumap RL (2004) Dj protein processing and Mn cluster assembly in light of the emerging photosystem II structure. Phys Chem Chem Phys 6 4803-4809... 

Michel, H., Deisenhofer, J. Relevance of the photosynthetic reaction center from purple bacteria to the structure of photosystem II. BicKhemistry 27 1-7, 1988. 

Hankamer, B., Barber,/, and Boekema, E. J., 1997. Structure and membrane organization of photosystem II in green plants. Annual Review of Plant Physiology and Plant Molecular Biology 48 641—671. 

Structure of the Photosystem II Antenna Xanthophylls in LHCII Structure.117... 

Biesiadka, J., Loll, B., Kern, J., Irrgang K/D. and Zouni, A. (2004). Crystal structure of cyanobacteria photosystem II at 3.2A resolution. Phys. Chem. Chem. Phys., 6, 4733-4736 Canfield, D.E., Habicht, K.S. and Thamdrup, B. (2000). The Achaean sulfur cycle and the early history of atmospheric oxygen. Science, 288, 658-661... 

H. Kuhl, J. Kruip, A. Seidler, A. Krieger-Liszkay, M. Bunker, D. Bald, J.A. Scheidig, M. Rogner (2000) Towards structural determination of the water-splitting enzyme. Purification, crystallization, and preliminary crystallographic studies of photosystem II from a thermophilic cyanobacterium. J. Biol. Chem., 275 20652-20659... 

Photosystem I is a membrane pigment-protein complex in green plants, algae as well as cyanobacteria, and undergoes redox reactions by using the electrons transferred from photosystem II (PS II) [1], These membrane proteins are considered to be especially interesting in the study of monomolecular assemblies, because their structure contains hydrophilic area that can interact with the subphase as well as hydrophobic domains that can interact either with each other or with detergent and lipids [2], Moreover, studies with such proteins directly at the air-water interface are expected to be a valuable approach for their two-dimensional crystallization. 

Zouni, A., H. T. Witt, J. Kern, P. Fromme, N. Krauss, W. Saenger and P. Orth (2001) Crystal structure of photosystem II from Synechococcus elongatus at 3.8 A resolution. Nature, 409 739-743... 

LuskinsPB, OatesT. Single molecule high-resolution structure and electron conduction of photosystem II from scanning tunneling microscopy and spectroscopy. Bio-chem Biophys Acta 1998 1409 1-11. 

LoU, B., Kern, J., Saenger, W., Zouni, A. and Biesiadka, J. (2005) Towards complete cofactor arrangement in the 3.0 A resolution structure of photosystem II, Nature, 438, 1040-1044. Miller, A.-F. (2004) Superoxide dismutases active sites that save, but a protein that kills, Curr. Opin. Chem. Biol., 8, 162-168. 

The present discussion is only concerned with the structure/redox capacity of the site responsible for the oxidation of water. The starting point is the evidence that the photosynthetic pathway is triggered by photooxidation of the chlorophylls in photosystem II. The need for chlorophylls to recover the electrons lost in photooxidation (in order to regenerate their ability to absorb light) induces water to undergo oxidation, according to ... 

The EXAFS of Mn in photosystem II looks very much like that of a mixed-valence di-/j-oxo-bridged Mn dimer model compound (33,35). In particular, the Mn-Mn distance of 2.7 A in photosystem II is characteristic of a di-/j-oxo-bridged structure. Recent EXAFS data have indicated that a second Mn-Mn distance of 3.3 A may also be present (37-38). Although a clear picture of all of the Mn-Mn distances is not yet available, the EXAFS results are consistent with a structure in which two di-/j-oxo bridged Mn dimers are present in close proximity. 

The Mn-Mn distance of 2.7 A determined by EXAFS is diagnostic of a di-/i-oxo-bridged Mn dimer in photosystem II (33,35). However, one could imagine a number of arrangements of the four Mn ions in photosystem II which contain a di-/i-oxo-bridged structure. Moreover, the observation of two different Mn-Mn distances by EXAFS, could only be accounted for by one of the following three arrangements of Mn a Mn trimer plus one isolated (more than 3.3 A away) Mn mononuclear center, two isolated inequivalent Mn dimers, or a Mn tetramer. 

I have presented an overview of the current state-of-the-art in studies of the Mn complex in photosystem II. There are many unresolved questions and a clear picture of the structure and function of Mn in photosynthetic water oxidation is still not available. One useful approach to help determine the structure of the Mn complex in photosystem II involves the synthesis and characterization of Mn model complexes for comparison with the properties of the Mn complex in photosystem II. Recently, several tetrameric high-valent Mn-oxo complexes have been reported (see the chapter in this volume by G. Christou). Further characterization of existing and new high-valent tetrameric Mn-oxo model complexes, especially EPR and EXAFS measurements, will no doubt help clarify the present uncertain picture of the structure of the Mn complex in photosystem II. 

Spin density, Fe—S dimers, 38 443-445 Spin-dependent delocalization, 47 39 Spin echo studies, photosystem II, 33 233-234 Spin eigenfunctions, 38 427 Spinels, 4 155, 20 143, 144 arrangement, 2 29-33 crystal structure of, 4 153 neutron diffraction studies on, 8 249-250 substitution of oxygen by fluorine, 20 145, 146... 

Simidjiev, L, Barzda, V., Mustardy, L., and Garab, G. 1997. Isolation of lamellar aggregates of the light-harvesting chlorophyll a/b protein complex of photosystem II with long-range chiral order and structural flexibility. Anal. Biochem. 250 169-75. 

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