Isolation and characterisation of an unusual antenna complex from the marine purple sulphur photosynthetic bacterium Chromatium purpuratum BN5500

doi:10.1016/0005-2728(90)90199-E

Biochimica et Biophysica Acta (BBA) - Bioenergetics

Volume 1019, Issue 3, 19 September 1990, Pages 239-244

https://doi.org/10.1016/0005-2728(90)90199-E Get rights and content

Abstract

The photosynthetic unit of the marinè purple sulphur bacterium Chromatium purpuratum has been fractionated into two components. It consists of a normal LH1-reaction centre ‘core’ complex together with a spectrally unusual B830 LH2 complex. The polypeptide composition and spectral properties of the B830-complex have been characterised.

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Cited by (29)

Energy transfer in an LH4-like light harvesting complex from the aerobic purple photosynthetic bacterium Roseobacter denitrificans
2011, Biochimica et Biophysica Acta - Bioenergetics
Citation Excerpt :
A spectrally similar complex B800–B830 was also found in Chromatium (Chr.) purpuratum [7]. In response to low light conditions, another purple bacterium, Chr.
A peripheral light-harvesting complex from the aerobic purple bacterium Roseobacter (R.) denitrificans was purified and its photophysical properties characterized. The complex contains two types of pigments, bacteriochlorophyll (BChl) a and the carotenoid (Car) spheroidenone and possesses unique spectroscopic properties. It appears to lack the B850 bacteriochlorophyll a Q_y band that is typical for similar light-harvesting complex 2 antennas. Circular dichroism and low temperature steady-state absorption spectroscopy revealed that the B850 band is present but is shifted significantly to shorter wavelengths and overlaps with the B800 band at room temperature. Such a spectral signature classifies this protein as a member of the light-harvesting complex 4 class of peripheral light-harvesting complexes, along with the previously known light-harvesting complex 4 from Rhodopseudomonas palustris. The influence of the spectral change on the light-harvesting ability was studied using steady-state absorption, fluorescence, circular dichroism, femtosecond and microsecond time-resolved absorption and time-resolved fluorescence spectroscopies. The results were compared to the properties of the similar (in pigment composition) light-harvesting complex 2 from aerobically grown Rhodobacter sphaeroides and are understood within the context of shared similarities and differences and the putative influence of the pigments on the protein structure and its properties.
Carotenoid-bacteriochlorophyll energy transfer in LH2 complexes studied with 10-fs time resolution
2006, Biophysical Journal
Citation Excerpt :
We therefore used chromatophore membranes rather than the isolated LH2 complex. Previous studies (34) showed that the LH2 complex represents >90% of the pigment-protein complexes in C. purpuratum membranes under the cell growth conditions used for our samples. In this case, no sample degradation was detected.
In this report, we present a study of carotenoid-bacteriochlorophyll energy transfer processes in two peripheral light-harvesting complexes (known as LH2) from purple bacteria. We use transient absorption spectroscopy with ≈10 fs temporal resolution, which is necessary to observe the very fast energy relaxation processes. By comparing excited-state dynamics of the carotenoids in organic solvents and inside the LH2 complexes, it has been possible to directly evaluate their energy transfer efficiency to the bacteriochlorophylls. In the case of okenone in the LH2 complex from Chromatium purpuratum, we obtained an energy transfer efficiency of η_ET2 = 63 ± 2.5% from the optically active excited state (S₂) and η_ET1 = 61 ± 2% from the optically dark state (S₁); for rhodopin glucoside contained in the LH2 complex from Rhodopseudomonas acidophila these values become η_ET2 = 49.5 ± 3.5% and η_ET1 = 5.1 ± 1%. The measurements also enabled us to observe vibrational energy relaxation in the carotenoids’ S₁ state and real-time collective vibrational coherence initiated by the ultrashort pump pulses. Our results are important for understanding the dynamics of early events of photosynthesis and relating it to the structural arrangement of the chromophores.
Circular dichroism of carotenoids in bacterial light-harvesting complexes: Experiments and modeling
2004, Biophysical Journal
Citation Excerpt :
acidophila strain 10050 and Rsp. molischianum were grown anaerobically in the light and harvested as previously reported (Cogdell and Thorber, 1979; Cogdell et al., 1983, 1990; Cogdell and Crofts, 1990; Evans et al., 1990; Cogdell and Hawthornthwaite, 1993; Halloren et al., 1995). Isolation and purification of the antenna complexes were performed as described in Cogdell and Hawthornthwaite (1993).
In this work we investigate the origin and characteristics of the circular dichroism (CD) spectrum of rhodopin glucoside and lycopene in the light-harvesting 2 complex of Rhodopseudomonas acidophila and Rhodospirillum molischianum, respectively. We successfully model their absorption and CD spectra based on the high-resolution structures. We assume that these spectra originate from seven interacting transition dipole moments: the first corresponds to the 0-0 transition of the carotenoid, whereas the remaining six represent higher vibronic components of the S₂ state. From the absorption spectra we get an estimate of the Franck-Condon factors of these transitions. Furthermore, we investigate the broadening mechanisms that lead to the final shape of the spectra and get an insight into the interaction energy between carotenoids. Finally, we examine the consequences of rotations of the carotenoid transition dipole moment and of deformations in the light-harvesting 2 complex rings. Comparison of the modeled carotenoid spectra with modeled spectra of the bacteriochlorophyll Q_Y region leads to a refinement of the modeling procedure and an improvement of all calculated results. We therefore propose that the combined carotenoid and bacteriochlorophyll CD can be used as an accurate reflection of the overall structure of the light-harvesting complexes.
Absorption and CD spectroscopy and modeling of various LH2 complexes from purple bacteria
2002, Biophysical Journal
Citation Excerpt :
The two LH2 complexes also differ in the carotenoid molecules which, however, have the same orientations in both structures with only minor deviations close to the B850 BChls. Earlier CD studies of purple bacterial antenna systems indicate that the types of LH2 complexes found can vary greatly (Cogdell and Scheer, 1985). Here we report the results of a comprehensive comparison study by means of absorption and circular dichroism spectroscopy of LH2 complexes from many different species.
The absorption (OD) and circular dichroism (CD) spectra of LH2 complexes from various purple bacteria have been measured and modeled. Based on the lineshapes of the spectra we can sort the LH2 complexes into two distinguishable groups: “acidophila”-like (type 1) and “molischianum”-like (type 2). Starting from the known geometric structures of Rhodopseudomonas (Rps.) acidophila and Rhodospirillum (Rsp.) molischianum we can model the OD and CD spectra of all species by just slightly varying some key parameters: the interaction strength, the energy difference of α- and β-bound B850 bacteriochlorophylls (BChls), the orientation of the B800 and B850 BChls, and the (in)homogeneous broadening. Although the ring size can vary, the data are consistent with all the LH2 complexes having basically very similar structures.
Biochemical and spectroscopic characterization of the reaction center-LH1 complex and the carotenoid-containing B820 subunit of Chromatium purpuratum
1994, BBA - Bioenergetics
Two complexes, the reaction center light-harvesting complex 1 (RC-LH1) and the B820 subunit of the LH1, have been isolated and characterized from the purple-sulfur photosynthetic bacterium Chromatium purpuratum. The RC-LH1 consists of the B870 antenna and a P-870 RC with an associated tetraheme cytochrome. This complex can be further fractionated to yield the B820 subunit of the LH1. The C. purpuratum B820 subunit is the first isolated from a purple-sulfur bacterium. It is also the first that retains its carotenoid absorption properties. CD spectra in the Q_y region of bacteriochlorophyll a in both the RC-LH1 and the B820 subunit are bathochromically shifted as compared to other such complexes. Comparison of the sequence of the LH1β polypeptide to other LH1βs reveals the presence of additional aromatic amino acids in the vicinity of both of the conserved histidines in the C. purpuratum β polypeptide. The CD spectra of these C. purpuratum pigment-protein complexes can be interpreted in terms of exciton interaction between bacteriochlorophylls in the B820 subunit of the LH1 and in the B870, with additional spectral characteristics arising from interactions of the pigments with their protein environment.
Structure, function and organization of antenna polypeptides and antenna complexes from the three families of Rhodospirillaneae
1992, Journal of Photochemistry and Photobiology, B: Biology
Comparative primary structural analysis of polypeptides from antenna complexes from species of the three families of Rhodospirillaneae indicates the structural principles responsible for the formation of spectrally distinct light-harvesting complexes. In many of the characterized antenna systems the basic structural minimal unit is an α/β polypeptide pair. Specific clusters of amino acid residues, in particular aromatic residues in the C-terminal domain, identify the antenna polypeptides to specific types of antenna systems, such as B880 (strong circular dichroism (CD)), B870 (weak CD), B800–850 (high), B800–850 (low) or B800–820. The core complex B880 (B1020) of species from Ectothiorhodospiraceae and Chromatiaceae apparently consists of four (α₁α₂β₁β₂) or three (2αβ₁β₂) chemically dissimilar antenna polypeptides respectively. There is good evidence that the so-called variable antenna complexes, such as the B800–850 (high), B800–850 (low) or B800–820 of Rp. acidophila, Rp. palustris and Cr. vinosum, are comprised of multiple forms of peripheral light-harvesting polypeptides. Structural similarities between prokaryotic and eukaryotic antenna polypeptides are discussed in terms of similar pigment organization.
The structural basis for the strict organization of pigment molecules (bacteriochlorophyll (BChl) cluster) in the antenna system of purple bacteria is the hierarchical organization of the α- and β-antenna polypeptides within and between the antenna complexes. On the basis of the three-domain structure of the antenna polypeptides with the central hydrophobic domain, forming a transmembrane α helix, possible arrangements of the antenna polypeptides in the three-dimensional structure of core and peripheral antenna complexes are discussed. Important structural and functional features of these polypeptides and therefore of the BChl cluster are the α/β heterodimers, the α₂,β₂ basic units and cyclic arrangements of these basic units. Equally important for the formation of the antenna complexes or the entire antenna are polypeptide-polypeptide, pigment-pigment and pigment-polypeptide interactions.

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Regular paperIsolation and characterisation of an unusual antenna complex from the marine purple sulphur photosynthetic bacterium Chromatium purpuratum BN5500

Abstract

Zent.bl. Bakteriol. Parasitenkd. Infekt. Krankh. Hyg. Bakt. I Corg.

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Biochim. Biophys. Acta

Methods Enzymol.

Biochim. Biophys. Acta

Encycl. Pl. Physiol.

Regular paper
Isolation and characterisation of an unusual antenna complex from the marine purple sulphur photosynthetic bacterium Chromatium purpuratum BN5500