Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroides

Francia, Francesco; Wang, Jun; Zischka, Hans; Venturoli, Giovanni; Oesterhelt, Dieter

doi:10.1046/j.1432-1327.2002.02834.x

Cited by 16 publications

(28 citation statements)

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“…The final component of the core complex, PufX, is responsible for the formation of core complex dimers within the chromatophore membrane (Francia et al ., 1999; 2002; Siebert et al ., 2004; Qian et al ., 2005; Holden‐Dye et al ., 2008; Ratcliffe et al ., 2011). PufX was identified in the qualitative data only in the ICM fraction (Table S1C) in agreement with Zeng et al .…”

Section: Resultsmentioning

confidence: 99%

Quantitative proteomic analysis of intracytoplasmic membrane development in Rhodobacter sphaeroides

Jackson

Lewis

Tucker

et al. 2012

Molecular Microbiology

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SummaryThe purple phototrophic bacteria elaborate a specialized intracytoplasmic membrane (ICM) system for the conversion of solar energy to ATP. Previous radiolabelling and ultrastructural experiments have shown that ICM assembly in Rhodobacter sphaeroides is initiated at indentations of the cytoplasmic membrane, termed UPB. Here, we report proteomic analyses of precursor (UPB) and mature (ICM) fractions. Qualitative data identified 387 proteins, only 43 of which were found in the ICM, reflecting its specialized role within the cell, the conversion of light into chemical energy; 236 proteins were found in the significantly more complex UPB proteome. Metabolic labelling was used to quantify the relative distribution of 173 proteins between the UPB and ICM fractions. Quantification reveals new information on assembly of the RC-LH1-PufX, ATP synthase and NAD(P)H transhydrogenase complexes, as well as showing that the UPB is enriched in enzymes for lipid, carbohydrate and amino acid metabolism, tetrapyrrole biosynthesis and proteins representing a wide range of other metabolic and biosynthetic functions. Proteins involved in light harvesting, photochemistry, electron transport and ATP synthesis are all enriched in ICM, consistent with the spatial proximity of energy capturing and transducing functions. These data provide further support to the developmental precursor-product relationship between UPB and ICM.

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Section: Resultsmentioning

confidence: 99%

Quantitative proteomic analysis of intracytoplasmic membrane development in Rhodobacter sphaeroides

Jackson

Lewis

Tucker

et al. 2012

Molecular Microbiology

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“…Besides chromatophores, we examine the quinone content and distribution in purified RC⅐LH1 complexes. Dimeric and monomeric preparations of such complexes have been characterized biochemically (24,27) and structurally (25), but only one functional study has been published thus far (28). We show that the complexes retain quite a large fraction (Ϸ25-30%) of the quinone pool present in chromatophores.…”

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confidence: 89%

“…A small polypeptide, PufX, appears to play a key role in determining the structural organization. In its absence, the RC⅐LH1 complexes adopt a monomeric conformation with a closed LH1 ring of 16 ␣␤-heterodimers (23)(24)(25)27).…”

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confidence: 99%

Functional Consequences of the Organization of the Photosynthetic Apparatus in Rhodobacter sphaeroides

Comayras

Jungas

Lavergne

2005

Journal of Biological Chemistry

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The purpose of this study was to gain information on the functional consequences of the supramolecular organization of the photosynthetic apparatus in the bacterium Rhodobacter sphaeroides. Isolated complexes of the reaction center (RC) with its core antenna ring (light-harvesting complex 1 (LH1)) were studied in their dimeric (native) form or as monomers with respect to excitation transfer and distribution of the quinone pool. Similar issues were examined in chromatophore membranes. The relationship between the fluorescence yield and the amount of closed centers is indicative of a very efficient excitation transfer between the two monomers in isolated dimeric complexes. A similar dependence was observed in chromatophores, suggesting that excitation transfer in vivo from a closed RC⅐LH1 unit is also essentially directed to its partner in the dimer. The isolated complexes were found to retain 25-30% of the endogenous quinone acceptor pool, and the distribution of this pool among the complexes suggests a cooperative character for the association of quinones with the protein complexes. In chromatophores, the decrease in the amount of photoreducible quinones when inhibiting a fraction of the centers implies a confinement of the quinone pool over small domains, including one to six reaction centers. We suggest that the crowding of membrane proteins may not be the sole reason for quinone confinement and that a quinone-rich region is formed around the RC⅐LH1 complexes.

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“…In this context, the structural analysis of Rhodobacter core complexes is of particular interest, because it is the only species in which a small trans-membrane protein named PufX has been identified as crucial for bacterial growth under anaerobic photosynthetic conditions and for the fast exchange of quinones between the RC and the cytochrome bc 1 complex (11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Biochemical studies have shown that PufX-containing core complexes could be isolated from Rhodobacter sphaeroides membranes as dimeric structures with a 1:1 PufX/RC stoichiometry and a decreased number of LH1-associated bacteriochlorophylls per RC (21).…”

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Structure of the Dimeric PufX-containing Core Complex of Rhodobacter blasticus by in Situ Atomic Force Microscopy

Scheuring¹,

Busselez²,

Lévy³

2005

Journal of Biological Chemistry

122

125

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We have studied photosynthetic membranes of wild type Rhodobacter blasticus, a closely related strain to the well studied Rhodobacter sphaeroides, using atomic force microscopy. High-resolution atomic force microscopy topographs of both cytoplasmic and periplasmic surfaces of LH2 and RC-LH1-PufX (RC, reaction center) complexes were acquired in situ. The LH2 is a nonameric ring inserted into the membrane with the 9-fold axis perpendicular to the plane. The core complex is an S-shaped dimer composed of two RCs, each encircled by 13 LH1 ␣/␤-heterodimers, and two PufXs. The LH1 assembly is an open ellipse with a topography-free gap of ϳ25 Å. The two PufXs, one of each core, are located at the dimer center. Based on our data, we propose a model of the core complex, which provides explanation for the PufX-induced dimerization of the Rhodobacter core complex. The Q B site is located facing a ϳ25-Å wide gap within LH1, explaining the PufXfavored quinone passage in and out of the core complex.In purple photosynthetic bacteria, highly organized transmembrane pigment-protein complexes perform absorption of light and its conversion into chemical energy. Two light harvesting (LH) 1 complexes, LH2 and LH1, ensure the collection of light. The excitation energy is funneled toward the special pair (P) of bacteriochlorophylls in the reaction center (RC) followed by an electron transfer from P to the ubiquinone (Q) acceptors, Q A and Q B . After two photoreactions and proton captures, ubiquinol (Q-H 2 ) is formed at the Q B site that dissociates from the RC into the membrane. The cytochrome bc 1 complex utilizes Q-H 2 and oxidized cytochrome c 2 as reductant and oxidant, respectively. The net result is a cyclic electron transfer that promotes the formation of a proton gradient across the membrane, which is utilized for ATP synthesis by the F 1 F 0 -ATP synthase (for review see Ref. 1).The description of the bacterial photosynthetic apparatus at atomic level is nearly complete. Two RC structures (2-4), two LH2 structures (5, 6), and the structure of the homologue bc 1 complex from the respiratory chain (7) are known. However, the structure of the core complex composed of the LH1 and the RC remains undetermined.Over the last two years, the data of core complexes of Rhodospirillum (Rsp.) rubrum (8), Blastochloris viridis (9), and Rhodopseudomonas (Rps.) palustris (10) have been acquired at a resolution sufficient to delineate the LH1 subunit arrangement around the RC. Whereas Rsp. rubrum and B. viridis have monomeric core complexes with 16 LH1 subunits arranged around the RC, Rps. palustris has 15 LH1 subunits plus an unknown polypeptide forming a single trans-membrane helix. The closed architecture of the LH1 assembly raised the question of the quinone exchange through the LH1 assembly between the RC and the cytochrome bc 1 .In this context, the structural analysis of Rhodobacter core complexes is of particular interest, because it is the only species in which a small trans-membrane protein named PufX has been identified as crucial ...

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Role of the N- and C-terminal regions of the PufX protein in the structural organization of the photosynthetic core complex of Rhodobacter sphaeroides

Cited by 16 publications

References 0 publications

Quantitative proteomic analysis of intracytoplasmic membrane development in Rhodobacter sphaeroides

Quantitative proteomic analysis of intracytoplasmic membrane development in Rhodobacter sphaeroides

Functional Consequences of the Organization of the Photosynthetic Apparatus in Rhodobacter sphaeroides

Structure of the Dimeric PufX-containing Core Complex of Rhodobacter blasticus by in Situ Atomic Force Microscopy

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