Circular Symmetry of the Light-Harvesting 1 Complex from <i>Rhodospirillum rubrum</i> Is Not Perturbed by Interaction with the Reaction Center

Gerken, Uwe; Lupo, Domenico; Tietz, C.; Wrachtrup, Jörg; Ghosh, Robin

doi:10.1021/bi034969m

Cited by 33 publications

(33 citation statements)

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“…The absence of this deactivation channel for the RC-subunit deletion strains confirms the assignment of this essential quenching mechanism. Taken together, these results are consistent with the hypothesis derived from single molecule fluorescence data (Gerken et al 2003) as well as from 2D crystals in vitro (Karrasch et al 1995;Jamieson et al 2002), that for the R. rubrum PSU, the presence of a RC has no effect upon the overall pigment organization of the LH1 complex in vivo. and, SPUHK1 as viewed from the periplasmic surface.…”

Section: Discussionsupporting

confidence: 91%

“…A complication here, in addition to the low resolution of the data, is that the R. blasticus PSU appears to be an RC-LH1 dimer, also containing the PufX polypeptide, which has been implicated in quinone transfer across the LH1 ring Wachtveitl et al 1993), whereas the R. rubrum PSU, which lacks PufX (Bèlanger et al 1988), appears to be a closed unit. On the other hand, SM spectroscopic studies performed on PSUs isolated by the Ghosh group have indicated no perturbation of the LH1 circular symmetry due to the presence of an RC (Gerken et al 2003) either when solubilized in detergent or reconstituted into bilayer membranes. Nevertheless, both the low resolution (4 Å ) crystal structure (Roszak et al 2003) and SM spectroscopy (Richter et al 2007) of a detergent-solubilized PSU from Rhodopseudomonas palustris, as well as AFM images of the PSU in intact membranes of Rhodospirillum photometricum (Scheuring et al 2004) also indicate an elliptical geometry of the LH1 ring.…”

Section: Introductionmentioning

confidence: 99%

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Excitation energy pathways in the photosynthetic units of reaction center LM- and H-subunit deletion mutants of Rhodospirillum rubrum

et al. 2010

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Light-induced reaction dynamics of isolated photosynthetic membranes obtained from wild-type (WT) and reaction center (RC)-subunit deletion strains SPUHK1 (an H-subunit deletion mutant) and SK Delta LM (an (L+M) deletion mutant) of the purple non-sulphur bacterium Rhodospirillum rubrum have been investigated by femtosecond transient absorption spectroscopy. Upon excitation of the spirilloxanthin (Spx) S(2) state at 546 nm, of the bacteriochlorophyll Soret band at 388 nm and probing spectral regions, which are characteristic for carotenoids, similar dynamics in the SPUHK1, SK Delta LM and WT strains could be observed. The excitation of Spx S(2) is followed by the simultaneous population of the lower singlet excited states S(1) and S* which decay with lifetimes of 1.4 and 5 ps, respectively for the mutants, and 1.4 and 4 ps, respectively, for the wild-type. The excitation of the BChl Soret band is followed by relaxation into BChl lower excited states which compete with excitation energy transfer BChl-to-Spx. The deexcitation pathway BChl(Soret) --> Spx(S(2)) --> Spx(S(1)) occurs with the same transition rate for all investigated samples (WT, SPUHK1 and SK Delta LM). The kinetic traces measured for the Spx S(1) --> S(N) transition display similar behaviour for all samples showing a positive signal which increases within the first 400 fs (i.e. the time needed for the excitation energy to reach the Spx S(1) excited state) and decays with a lifetime of about 1.5 ps. This suggests that the Spx excited state dynamics in the investigated complexes do not differ significantly. Moreover, a longer excited state lifetime of BChl for SPUHK1 in comparison to WT was observed, consistent with a photochemical quenching channel present in the presence of RC. For long delay times, photobleaching of the RC special pair and an electrochromic blue shift of the monomeric BChl a can be observed only for the WT but not for the mutants. The close similarity of the excited state decay processes of all strains indicates that the pigment geometry of the LH1 complex in native membranes is unaffected by the presence of an RC and allows us to draw a model representation of the WT, SK Delta LM and SPUHK1 PSU complexes.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Excitation energy pathways in the photosynthetic units of reaction center LM- and H-subunit deletion mutants of Rhodospirillum rubrum

et al. 2010

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“…However, adoption of this shape by the encircling LH1 ring depends on external packing constraints. When these packing forces are evenly applied, as in the tetragonal crystals of Jamieson et al (6), or absent, as in solution (30), then they can be circular. In contrast, when packing forces are anisotropic, the complex can be squeezed so that it adopts an elliptical shape (6).…”

Section: Discussionmentioning

confidence: 99%

Structural Analysis of the Reaction Center Light-harvesting Complex I Photosynthetic Core Complex of Rhodospirillum rubrum Using Atomic Force Microscopy

Fotiadis

Qian

Philippsen

et al. 2004

Journal of Biological Chemistry

146

123

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The bacterium Rhodospirillum rubrum contains a simple photosynthetic system, in which the reaction center (RC) receives energy from the light-harvesting (LH1) complex. We have used high-resolution atomic force microscopy (AFM) to image two-dimensional crystals of the RC-LH1 complex of R. rubrum. The AFM topographs show that the RC-LH1 complex is ϳ94 Å in height, the RC-H subunit protrudes from the cytoplasmic face of the membrane by 40 Å, and it sits 21 Å above the highest point of the surrounding LH1 ring. In contrast, the RC on the periplasmic side is at a lower level than LH1, which protrudes from the membrane by 12 Å. The RC-LH1 complex can adopt an irregular shape in regions of uneven packing forces in the crystal; this reflects a likely flexibility in the natural membrane, which might be functionally important by allowing the export of quinol formed as a result of RC photochemistry. Nanodissection of the RC by the AFM tip removes the RC-H subunit and reveals the underlying RC-L and -M subunits. LH1 complexes completely lacking the RC were also found, providing ideal conditions for imaging both rings of LH1 polypeptides for the first time by AFM. In addition, we demonstrate the ellipticity of the LH1 ring at the cytoplasmic and periplasmic sides of the membrane, in both the presence and absence of the RC. These AFM measurements have been reconciled with previous electron microscopy and NMR data to produce a model of the RC-LH1 complex.Photosynthetic organisms harvest light energy and convert it to a chemically useful form, using light-harvesting (LH) 1 and reaction center (RC) complexes. This coupling between LH and RC complexes involves close physical proximity because of the distance term governing energy transfer between the complexes (1). In the purple photosynthetic bacteria, the reaction center receives energy from the LH1 complex (reviewed in Ref.2). This particular energy transfer step, which takes ϳ35-45 ps (3), is important, because it is the rate-limiting step in the process of trapping light energy in photosynthetic bacteria (4).In view of the value of the RC-LH1 complex as a model for coupled light-harvesting energy transfer and photochemistry, structural information on the association between LH1 and RC complexes is required. Rhodospirillum rubrum, which represents one of the simplest possible photosynthetic systems, is valuable in this respect. A recent cryo-electron microscopy (EM) study of the RC-LH1 complex of R. rubrum, which built upon earlier work on the LH1-only (no RC) complex (5), shows that the RC complex is surrounded by a ring of 16␣ and 16␤ LH1 subunits, which would correspond to 32 bacteriochlorophylls (BChls) (6). This structure provides a rationale for the rate-limiting energy transfer step, because the ϳ45 Å distance from LH1 BChls to the special pair BChls of the RC is considerable (5, 6). This should be viewed in the context of known energy transfer steps and distances in these bacteria: for example, the internal transfer of energy in ϳ0.5-1 ps between the B800 and B850 BCh...

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“…In other words cryogenic conditions are well suited to obtain a good approximation of the electronic structure of biomolecules. Such lowtemperature experiments revealed valuable information about the character of the electronically excited states of the antenna complexes (Tietz et al 1999;Van Oijen et al 1999;Ketelaars et al 2002Ketelaars et al , 2006Gerken et al 2003;De Ruijter et al 2004Hofmann et al 2004a;Richter et al 2007b). The robustness of the light-harvesting process in purple bacteria has been demonstrated by the observation of the excitation-energy transfer within a single self-aggregated photosynthetic unit in a non-membrane environment under cryogenic conditions (Hofmann et al 2003a).…”

Section: Pigment-protein Complexes From Purple Bacteriamentioning

confidence: 99%

Low-temperature single-molecule spectroscopy on photosynthetic pigment–protein complexes from purple bacteria

Oellerich

Köhler

2009

Photosynth Res

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The primary reactions of purple bacterial photosynthesis take place within two well characterized pigment-protein complexes, the core Reaction Center-Light Harvesting 1 (RC-LH1) complex and the more peripheral Light Harvesting 2 (LH2) complex. These antenna complexes serve to absorb incident solar radiation and to transfer it to the reaction-centers, where it is used to 'power' the photosynthetic redox reaction. This review provides an overview of how the character of the electronically excited states of these pigment-protein complexes are determined by quantum mechanics and how the respective spectral signatures can be observed by single-molecule spectroscopy.

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Circular Symmetry of the Light-Harvesting 1 Complex from Rhodospirillum rubrum Is Not Perturbed by Interaction with the Reaction Center

Cited by 33 publications

References 44 publications

Excitation energy pathways in the photosynthetic units of reaction center LM- and H-subunit deletion mutants of Rhodospirillum rubrum

Excitation energy pathways in the photosynthetic units of reaction center LM- and H-subunit deletion mutants of Rhodospirillum rubrum

Structural Analysis of the Reaction Center Light-harvesting Complex I Photosynthetic Core Complex of Rhodospirillum rubrum Using Atomic Force Microscopy

Low-temperature single-molecule spectroscopy on photosynthetic pigment–protein complexes from purple bacteria

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