Three-dimensional structures of photosynthetic reaction centers |
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Authors: | C Roy D Lancaster Hartmut Michel |
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Institution: | (1) Max-Planck-Institut für Biophysik, Abteilung Molekulare Membranbiologie, Heinrich-Hoffmannstr. 7, D-60528 Frankfurt am Main, Germany |
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Abstract: | In this article, the three-dimensional structures of photosynthetic reaction centers (RCs) are presented mainly on the basis of the X-ray crystal structures of the RCs from the purple bacteria Rhodopseudomonas (Rp.) viridis and Rhodobacter (Rb.) sphaeroides. In contrast to earlier comparisons and on the basis of the best-defined Rb. sphaeroides structure, a number of the reported differences between the structures cannot be confirmed. However, there are small conformational differences which might provide a basis for the explanation of observed spectral and functional discrepancies between the two species.A particular focus in this review is on the binding site of the secondary quinone (QB), where electron transfer is coupled to the uptake of protons from the cytoplasm. For the discussion of the QB site, a number of newlydetermined coordinate sets of Rp. viridis RCs modified at the QB site have been included. In addition, chains of ordered water molecules are found leading from the cytoplasm to the QB site in the best-defined structures of both Rp. viridis and Rb. sphaeroides RCs.Abbreviations BA
accessory bacteriochlorophyll in the active branch
- BB
accessory bacteriochlorophyll in the inactive branch
- D
primary electron donor ( special pair )
- DL
special pair bacteriochorophyll bound by the L subunit
- DM
special pair bacteriochorophyll bound by the M subunit
- QA
primary electron acceptor quinone
- QB
secondary electron acceptor quinone
- RC
reaction center
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Rb.
Rhodobacter
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Rp.
Rhodopseudomonas
- A
bacteriopheophytin in the active branch
- B
bacteriopheophytin in the inactive branch |
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Keywords: | purple bacteria QB Rhodobacter sphaeroides Rhodopseudomonas viridis secondary quinone water chain |
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