Incorporation of spheroidene and spheroidenone into light-harvesting complexes from purple sulfur bacteria

With the recent developments in the field of free-electron-laser-based serial femtosecond crystallography, the necessity to obtain a large number of high-quality crystals has emerged. In this work crystallization techniques were selected, tested and optimized for the lipid mesophase crystallization of the Rhodobacter sphaeroides membrane pigment-protein complex, known as the photosynthetic reaction center (RC). Novel approaches for lipid sponge phase crystallization in comparatively large volumes using Hamilton gas-tight glass syringes and plastic pipetting tips are described. An analysis of RC crystal structures obtained by lipid mesophase crystallization revealed non-native ligands that displaced the native electron-transfer cofactors (carotenoid spheroidene and a ubiquinone molecule) from their binding pockets. These ligands were identified and were found to be lipids that are major mesophase components. The selection of distinct co-crystallization conditions with the missing cofactors facilitated the restoration of spheroidene in its binding site.

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“…To dissolve spheroidene we used acetone. The extraction method for this pigment is described in the work by Ashikhmin et al (2017).…”

Section: Preparation Of Spheroidene and Ubiquinonementioning

confidence: 99%

Novel approaches for the lipid sponge phase crystallization of the Rhodobacter sphaeroides photosynthetic reaction center

Selikhanov

Fufina

Vasilieva

et al. 2020

Int Union Crystallogr J

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“…The effects of the conjugation length in Crt on the efficiency of intra-complex Crt → BChl energy transfer were examined, comparing the native LH1, which contains Spx, and LH1 reconstituted with Sph (Sph-LH1). The LH capability of these two Crts, incorporated into the same BChl a -polypeptide matrix, was determined using a previously described method [33], by comparing the intensities of the fractional absorption and fluorescence excitation spectra normalized to the BChl Q X band (Figure 5). The ratio of spectral integrals between 430 and 560 nm gives an estimate of the efficiency of excitation energy transfer.…”

Section: Resultsmentioning

confidence: 99%

“…In effect, electrostatic interactions between the interfaces of the transmembrane helical fragments of the α/β polypeptides are greatly intensified and the thermodynamics of LH1 assembly in a micellar medium is under the strong control of co-solvent and the Crt cofactor [18,38]. A similar stabilizing effect of Crts was found in LH2 [33]. In the absence of these external factors, the interaction energy (ΔH°) between the LH1 polypeptides equals −580 kJ/mol.…”

Section: Discussionmentioning

confidence: 97%

“…The most plausible reason for this dependence is the shortening of the lifetime of the S 2 donor state of Crt as n is increasing [16,40]. Efficient and fast intra-complex Crt → BChl energy transfer takes place only if Crt is incorporated into properly folded LH1 [17] and hence its efficiency, being strongly dependent on the mutual orientation and inter-pigment distances [33], can be regarded as an indicator that the assembled antenna complex is functioning properly. A very high efficiency of energy transfer in Sph-LH1, reaching 90%, confirms that a fully functional LH1 complex incorporating the non-native Crts has been reconstituted [16,23].…”

Section: Discussionmentioning

confidence: 99%

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Tuning the Photophysical Features of Self-Assembling Photoactive Polypeptides for Light-Harvesting

et al. 2019

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The LH1 complex is the major light-harvesting antenna of purple photosynthetic bacteria. Its role is to capture photons, and then store them and transfer the excitation energy to the photosynthetic reaction center. The structure of LH1 is modular and it cooperatively self-assembles from the subunits composed of short transmembrane polypeptides that reversibly bind the photoactive cofactors: bacteriochlorophyll and carotenoid. LH1 assembly, the intra-complex interactions and the light-harvesting features of LH1 can be controlled in micellar media by varying the surfactant concentration and by adding carotenoid and/or a co-solvent. By exploiting this approach, we can manipulate the size of the assembly, the intensity of light absorption, and the energy and lifetime of its first excited singlet state. For instance, via the introduction of Ni-substituted bacteriochlorophyll into LH1, the lifetime of this electronic state of the antenna can be shortened by almost three orders of magnitude. On the other hand, via the exchange of carotenoid, light absorption in the visible range can be tuned. These results show how in a relatively simple self-assembling pigment-polypeptide system a sophisticated functional tuning can be achieved and thus they provide guidelines for the construction of bio-inspired photoactive nanodevices.

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“…From neurosporene (Figure 1), the main pathway can continue to lycopene, or two more different branches can be distinguished: one of them for the synthesis of zeacarotene and the other one the spheroidene biosynthesis pathway [37]. The compounds made through the spheroidene biosynthesis pathway are mainly related to antenna complexes of sulfur photosynthetic bacteria [38,39].…”

Section: Reconstruction Of a Metabolic Map For Global Carotenogenesismentioning

confidence: 99%

Deciphering Pathways for Carotenogenesis in Haloarchaea

et al. 2020

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Bacterioruberin and its derivatives have been described as the major carotenoids produced by haloarchaea (halophilic microbes belonging to the Archaea domain). Recently, different works have revealed that some haloarchaea synthetize other carotenoids at very low concentrations, like lycopene, lycopersene, cis- and trans-phytoene, cis- and trans-phytofluene, neo-β-carotene, and neo-α-carotene. However, there is still controversy about the nature of the pathways for carotenogenesis in haloarchaea. During the last decade, the number of haloarchaeal genomes fully sequenced and assembled has increased significantly. Although some of these genomes are not fully annotated, and many others are drafts, this information provides a new approach to exploring the capability of haloarchaea to produce carotenoids. This work conducts a deeply bioinformatic analysis to establish a hypothetical metabolic map connecting all the potential pathways involved in carotenogenesis in haloarchaea. Special interest has been focused on the synthesis of bacterioruberin in members of the Haloferax genus. The main finding is that in almost all the genus analyzed, a functioning alternative mevalonic acid (MVA) pathway provides isopentenyl pyrophosphate (IPP) in haloarchaea. Then, the main branch to synthesized carotenoids proceeds up to lycopene from which β-carotene or bacterioruberin (and its precursors: monoanhydrobacterioriberin, bisanhydrobacterioruberin, dihydrobisanhydrobacteriuberin, isopentenyldehydrorhodopsin, and dihydroisopenthenyldehydrorhodopsin) can be made.

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Incorporation of spheroidene and spheroidenone into light-harvesting complexes from purple sulfur bacteria

Cited by 37 publications

References 53 publications

Novel approaches for the lipid sponge phase crystallization of the Rhodobacter sphaeroides photosynthetic reaction center

Novel approaches for the lipid sponge phase crystallization of the Rhodobacter sphaeroides photosynthetic reaction center

Tuning the Photophysical Features of Self-Assembling Photoactive Polypeptides for Light-Harvesting

Deciphering Pathways for Carotenogenesis in Haloarchaea

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