TAILIEUCHUNG - Báo cáo khoa học: Structural characterization of photosystem II complex from red alga Porphyridium cruentum retaining extrinsic subunits of the oxygen-evolving complex

The structure of photosystem II (PSII) complex isolated from thylakoid membranes of the red alga Porphyridium cruentum was investigated using electron microscopy fol-lowed by single particle image analysis. The dimeric com-plexes observed contain all major PSII subunits (CP47, CP43, D1 and D2 proteins) as well as the extrinsic proteins (33 kDa, 12 kDa and the cytochromec550 ) of the oxygen-evolvingcomplex (OEC) of PSII, encodedby thepsbO,psbU andpsbVgenes, respectively. | Eur. J. Biochem. 271 2967-2975 2004 FEBS 2004 doi Structural characterization of photosystem II complex from red alga Porphyridium cruentum retaining extrinsic subunits of the oxygen-evolving complex Ladislav Bumba1 2 Helena Havelkova-Dousova3 4 Michal Husak4 and Frantisek Vacha2 4 1 Faculty of Biological Sciences University of South Bohemia Ceske Budejovice 2Institute of Plant Molecular Biology Academy of Sciences of the Czech Republic Ceske Budejovice 3 Laboratory of Photosynthesis Institute of Microbiology Academy of Sciences of the Czech Republic Trebon 4Institute of Physical Biology University of South Bohemia Ceske Budejovice Czech Republic The structure of photosystem II PSII complex isolated from thylakoid membranes of the red alga Porphyridium cruentum was investigated using electron microscopy followed by single particle image analysis. The dimeric complexes observed contain all major PSII subunits CP47 CP43 D1 and D2 proteins as well as the extrinsic proteins 33 kDa 12 kDa and the cytochrome c550 of the oxygenevolving complex OEC of PSII encoded by thepsbO psbU andpsbVgenes respectively. The single particle analysis of the top-view projections revealed the PSII complex to have maximal dimensions of 22 X 15 nm. The analysis of the side-view projections shows a maximal thickness of the PSII complex of about 9 nm including the densities on the lum-enal surface that has been attributed to the proteins of the OEC complex. These results clearly demonstrate that the red algal PSII complex is structurally very similar to that of cyanobacteria and to the PSII core complex of higher plants. In addition the arrangement of the OEC proteins on the lumenal surface of the PSII complex is consistent to that obtained by X-ray crystallography of cyanobacterial PSII. Keywords electron microscopy membrane protein photosynthesis photosystem II single particle image analysis. Red algae are evolutionarily one of the most primitive eukaryotic .

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