Structural Analysis of Photosystem II: Comparative Study of Cyanobacterial and Higher Plant Photosystem II Complexes |
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| Authors: | Lorenz Hasler,Demetrios Ghanotakis,Bettina Fedtke,Aspasia Spyridaki,Mette Miller,Shirley A. Mü ller,Andreas Engel,Georgios Tsiotis |
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| Affiliation: | aM. E. Müller Institute for Microscopic Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056, Basel, Switzerland;bDepartment of Chemistry, University of Crete, P.O. Box 1470, 71409, Iraklion, Crete, Greece;cM. E. Müller Institute for Microscopic Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056, Basel, Switzerland;dDepartment of Chemistry, University of Crete, P.O. Box 1470, 71409, Iraklion, Crete, Greece;eInstitute of Biochemistry, Odense University, Campusvej 55, 5230, Odense, Denmark;fM. E. Müller Institute for Microscopic Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056, Basel, Switzerland |
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| Abstract: | Oxygen evolving photosystem II (PSII-OEC) complexes and PSII core complexes were isolated from spinach and the thermophilic cyanobacteriumSynechococcussp. OD24 and characterized by gel electrophoresis, immunoblotting, and absorbance spectroscopy. The mass of the core complexes was determined by scanning transmission electron microscopy (STEM) and found to be 281 ± 65 kDa for spinach and 313 ± 52 kDa forSynechococcussp. OD24. The mass of the spinach PSII-OEC complex was 327 ± 64 kDa. Digital images of negatively stained PSII-OEC and PSII core complexes were recorded by STEM and analyzed by single particle averaging. All monomeric complexes showed similar morphologies and were of comparable length (14 nm) and width (10 nm). The averages revealed a pseudo-twofold symmetry axis, which is a prominent structural element of the monomeric form. Difference maps between the averaged projections of the oxygen evolving complexes and the core complexes from both species indicated where the 33-kDa extrinsic manganese stabilizing protein is bound. A symmetric organization of the PSII complex, with the PsbA and the PsbD proteins in the center and symmetrically arranged PsbB and PsbC proteins at the periphery of the monomeric complex, is proposed. |
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