The long-range supraorganization of the bacterial photosynthetic unit: A key role for PufX

Frese, Raoul N.; Olsen, John D.; Branvall, Rikard; Westerhuis, Willem H.J.; Hunter, C. Neil; Grondelle, Rienk van

doi:10.1073/pnas.090083797

Cited by 95 publications

(141 citation statements)

References 25 publications

Supporting

Mentioning

126

Contrasting

Order By: Relevance

“…This projection map revealed two C-shaped incomplete antenna rings each surrounding one RC. Finally, polarized spectroscopy of R. sphaeroides membranes containing or lacking PufX provided evidence that PufX induced a specific orientation of the RC in the LH1 ring as well as the formation of a long range order of LH1-RC core complexes (16,25). Taking together all of these considerations, PufX is thought to play a key role in the core complex.…”

mentioning

confidence: 94%

Structural Role of PufX in the Dimerization of the Photosynthetic Core Complex of Rhodobacter sphaeroides

Scheuring

Francia

Busselez

et al. 2004

Journal of Biological Chemistry

119

142

View full text Add to dashboard Cite

Monomeric and dimeric PufX-containing core complexes have been purified from membranes of wild-type Rhodobacter sphaeroides. Reconstitution of both samples by detergent removal in the presence of lipids leads to the formation of two-dimensional crystals constituted of dimeric core complexes. Two-dimensional crystals were further analyzed by cryoelectron microscopy and atomic force microscopy. A projection map at 26-Å resolution reveals that core complexes assemble in an "S"-shaped dimeric complex. Each core complex is composed of one reaction center, 12 light-harvesting 1 ␣/␤-heterodimers, and one PufX protein. The light-harvesting 1 assemblies are open with a gap of density of ϳ30-Å width and surround oriented reaction centers. A maximum density is found at the dimer junction. Based on the projection map, a model is proposed, in which the two PufX proteins are located at the dimer junction, consistent with the finding of dimerization of monomeric core complexes upon reconstitution. This localization of PufX in the core complex implies that PufX is the structural key for the dimer complex formation rather than a channel-forming protein for the exchange of ubiquinone/ubiquinol between the reaction center and the cytochrome bc1 complex.In purple photosynthetic bacteria, highly organized transmembrane pigment-protein complexes perform absorption of light and its conversion into chemical energy. Two light-harvesting complexes (LH), 1 LH2 and LH1, ensure the collection of light. Then the excitation energy is funneled toward the special pair of bacteriochlorophylls in the reaction center (RC), followed by an electron transfer from the special pair of bacteriochlorophylls to the ubiquinone (Q) acceptors Q A and Q B . After two photoreactions and proton captures, ubiquinol (QH 2 ) is formed at the Q B site that dissociates from the RC into the membrane. The bc 1 complex utilizes QH 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 F 1 F 0 -ATP synthase (for a review, see Ref. 1).The mechanisms of excitonic energy migration and photoinduced electron transfer have been studied in detail using biophysical approaches and analyzed at the molecular level following the resolution of the atomic structures of the RC (2), LH2 (3, 4), and the bc 1 complex (5). However, despite the wealth of information available on the individual proteins, their supramolecular organization in the membrane remains undetermined. A crucial issue is the spatial organization between LH1 and RC, forming the so-called core complex, in which the transformation of light energy into charge separation occurs. So far, no atomic model of the core complex is available. Early studies by various electron microscopy (EM) techniques of native membranes of Rhodopseudomonas viridis and Ectothiorhodospira halochloris have shown a single RC surrounded by a closed circle of light-harvesting molecule...

show abstract

mentioning

confidence: 94%

Structural Role of PufX in the Dimerization of the Photosynthetic Core Complex of Rhodobacter sphaeroides

Scheuring

Francia

Busselez

et al. 2004

Journal of Biological Chemistry

119

142

View full text Add to dashboard Cite

show abstract

“…Our understanding of the functionality of these systems improved even further when the long-range order of the LH1-RC complexes was reported for membranes of Rba. sphaeroides, where the gene PufX is expressed, 34,35 but LH2 was absent. Recently, Roszak et al (2003) 36 presented a RCLH1 crystal structure from Rps.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Effects of Different Carotenoids on the Absorption and CD Signals of Light Harvesting 1 Complexes

et al. 2006

Self Cite

View full text Add to dashboard Cite

Absorption and circular dichroism (CD) spectra of light-harvesting (LH)1 complexes from the purple bacteria Rhodobacter (Rba.) sphaeroides and Rhodospirillum (Rsp.) rubrum are presented. The complexes exhibit very low intensity, highly nonconservative, near-infrared (NIR) CD spectra. Absorption and CD spectra from several mutant and reconstituted LH1 complexes, with the carotenoid neurosporene and the precursor phytoene replacing the wild-type (WT) carotenoids, are also examined. The experiments show that the position of the carotenoid bands as well as the bacteriochlorophyll (BChl)/carotenoid ratio affect the NIR CD spectra: bluer bands and larger ratios make the NIR CD signal more conservative. Modeling results that support this finding are presented. This study, combined with the theoretical approach of the companion paper, where modeling of such complexes is presented and discussed in detail, provide a complete explanation of the origin of the nonconservative NIR CD spectra of LH1 and B820.

show abstract

“…In contrast to LH2, where highly resolved x-ray structures are available, the discussion in the literature about the structural properties of RC-LH1 is much more controversial (7,(19)(20)(21)(22)(23).…”

mentioning

confidence: 99%

Refinement of the x-ray structure of the RC–LH1 core complex from Rhodopseudomonas palustris by single-molecule spectroscopy

Richter

Baier

Southall

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

A unique combination of single-molecule spectroscopy with numerical simulations has allowed us to achieve a refined structural model for the bacteriochlorophyll a (BChl a) pigment arrangement in reaction center-light-harvesting 1 core complexes of Rhodopseudomonas palustris. Details in the optical spectra, such as spectral separation and mutual polarizations of spectral bands, are compared with results from numerical simulations for various models of the BChl a arrangement that were all well within the 4.8-Å limit of the accuracy of the available x-ray structure. The experimental data are consistent with a geometry where 15 BChl a dimers, each taken homologous to those from light-harvesting 2 complex from Rhodopseudomonas acidophila, are arranged in an overall elliptical structure featuring a gap on the long side of the ellipse.bacterial photosynthesis ͉ light harvesting ͉ supramolecular arrangement I n photosynthesis solar radiation is absorbed by the lightharvesting (LH) apparatus, and the excitation energy is then transferred efficiently to a reaction center (RC), where it is used to create a charge-separated state that ultimately drives all of the subsequent metabolic reactions. Most purple photosynthetic bacteria contain two types of antenna complexes, LH1 complex and LH2 complex (1, 2). The RC is closely associated with LH1, whereas LH2s are arranged around the perimeter of RC-LH1 in a 2D array, the structure of which depends on how the bacteria are grown (3-5). The progress made in high-resolution structural studies of the LH2s (6-9) has strongly stimulated research to understand the detailed mechanisms of the efficient energy transfer processes that take place in these antenna systems. The basic building block of LH2 is a protein heterodimer (␣␤), which accommodates three bacteriochlorophyll a (BChl a) pigments and one carotenoid molecule (8). Depending on the bacterial species LH2 consists either of eight or nine copies of these heterodimers, which are arranged in a ring-like structure. It has now been well established that the spatial arrangement of the pigments determines, to a large extent, the spectroscopic features of the complexes and that in these systems collective effects have to be considered to appropriately describe their electronically excited states (10-16). These effects lead to so-called Frenkel excitons, which arise from the interactions of the transition-dipole moments of the individual pigments and correspond to delocalized electronically excited states (17). Because the interaction strength between the individual pigments can be calculated on the basis of the available structural data, information about the pigment arrangement within the LH complexes becomes accessible via optical spectroscopy. From this perspective LH2 has served as a cornerstone for the development of a detailed understanding of structure-function relationships in such antenna systems (18).In contrast to LH2, where highly resolved x-ray structures are available, the discussion in the literature about the structural...

show abstract

The long-range supraorganization of the bacterial photosynthetic unit: A key role for PufX

Cited by 95 publications

References 25 publications

Structural Role of PufX in the Dimerization of the Photosynthetic Core Complex of Rhodobacter sphaeroides

Structural Role of PufX in the Dimerization of the Photosynthetic Core Complex of Rhodobacter sphaeroides

Investigation of the Effects of Different Carotenoids on the Absorption and CD Signals of Light Harvesting 1 Complexes

Refinement of the x-ray structure of the RC–LH1 core complex from Rhodopseudomonas palustris by single-molecule spectroscopy

Contact Info

Product

Resources

About