| Item type: | Article | ||||
|---|---|---|---|---|---|
| Journal or Publication Title: | Biochimica et Biophysica Acta (BBA) - Bioenergetics | ||||
| Publisher: | ELSEVIER SCIENCE BV | ||||
| Place of Publication: | AMSTERDAM | ||||
| Volume: | 1507 | ||||
| Number of Issue or Book Chapter: | 1-3 | ||||
| Page Range: | pp. 260-277 | ||||
| Date: | 2001 | ||||
| Institutions: | Biology, Preclinical Medicine > Institut für Pflanzenwissenschaften > Lehrstuhl für Zellbiologie und Pflanzenphysiologie (Prof. Dr. Klaus Grasser) | ||||
| Identification Number: |
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| Keywords: | PHOTOSYNTHETIC REACTION-CENTER; REACTION-CENTER COMPLEX; BIOSYNTHETIC-PATHWAY MUTANTS; CENTER CORE COMPLEXES; ELECTRON-PARAMAGNETIC-RESONANCE; CHLOROBIUM-TEPIDUM; PHOTOSYSTEM-I; PROSTHECOCHLORIS-AESTUARII; A(1) SITE; FOREIGN QUINONE; green sulfur bacteria; homodimeric P840 reaction center; FeS type reaction center; photosynthetic electron transport; energy transfer; bacteriochlorophyll protein; menaquinone; cytochrome; scanning transmission electron microscopy particle analysis | ||||
| Dewey Decimal Classification: | 500 Science > 570 Life sciences 500 Science > 580 Botanical sciences | ||||
| Status: | Published | ||||
| Refereed: | Yes, this version has been refereed | ||||
| Created at the University of Regensburg: | Yes | ||||
| Item ID: | 73393 |
Web of ScienceAbstract
The composition of the P840-reaction center complex (RC), energy and electron transfer within the RC, as well as its topographical organization and interaction with other components in the membrane of green sulfur bacteria are presented, and compared to the FeS-type reaction centers of Photosystem I and of Heliobacteria. The core of the RC is homodimeric, since pscA is the only gene found in the ...
Abstract
The composition of the P840-reaction center complex (RC), energy and electron transfer within the RC, as well as its topographical organization and interaction with other components in the membrane of green sulfur bacteria are presented, and compared to the FeS-type reaction centers of Photosystem I and of Heliobacteria. The core of the RC is homodimeric, since pscA is the only gene found in the genome of Chlorobium tepidum which resembles the genes psaA and -B for the heterodimeric core of Photosystem I. Functionally intact RC can be isolated from several species of green sulfur bacteria. It is generally composed of five subunits, PscA-D plus the BChl a-protein FMO. Functional cores, with PscA and PscB; only, can be isolated from Prostecochloris aestuarii. The PscA-dimer binds P840, a special pair of BChl a-molecules, the primary electron acceptor A(0), which is a Chl a-derivative and FeS-center F-X. An equivalent to the electron acceptor A, in Photosystem I, which is tightly bound phylloquinone acting between A(0) and F-X, is not required for forward electron transfer in the RC of green sulfur bacteria. This difference is reflected by different rates of electron transfer between A(0) and F-X in the two systems. The subunit PscB contains the two FeS-centers F-A and F-B. STEM particle analysis suggests that the core of the RC with PscA and PscB resembles the PsaAB/PsaC-core of the P700-reaction center in Photosystem 1. PscB may form a protrusion into the cytoplasmic space where reduction of ferredoxin occurs, with FMO trimers bound on both sides of this protrusion. Thus the subunit composition of the RC in vivo should be 2(FMO)(3)(PscA)(2)PscB(PScC)(2)PscD. Only 16 BChl a-, four Chl a-molecules and two carotenoids are bound to the RC-core, which is substantially less than its counterpart of Photosystem I, with 85 Chl a-molecules and 22 carotenoids. A total of 58 BChl a/RC are present in the membranes of green sulfur bacteria outside the chlorosomes, corresponding to two trimers of FMO (42 Bchl a) per RC (16 BChl a), The question whether the homodimeric RC is totally symmetric is still open. Furthermore, it is still unclear which cytochrome c is the physiological electron donor to P840(+). Also the way of NAD(+)-reduction is unknown, since a gene equivalent to ferredoxin-NADP(+) reductase is not present in the genome. (C) 2001 Elsevier Science B.V. All rights reserved.
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