Structure and Properties of the Bacteriochlorophyll Binding Site in Peripheral Light-Harvesting Complexes of Purple Bacteria

Sturgis, James N.; Jirsakova, Vladimira; Reiss‐Husson, Françoise; Cogdell, Richard J.; Robert, Bruno

doi:10.1021/bi00002a016

Cited by 74 publications

(111 citation statements)

References 20 publications

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“…In the resonance Raman spectrum of wt LH2, five bands in the carbonyl stretching modes region (1620 -1710 cm Ϫ1 ) are resolved (Fig. 5), similar to the findings of (42). The bands at 1627 and 1635 cm Ϫ1 have been attributed to the C-3 acetyl groups of the BChl-B850 (3).…”

Section: Fig 3 Optical Absorption and CD Spectra Of Wt Lh2 (-) Lh2supporting

confidence: 66%

“…The remaining bands have been attributed to the 13 1 keto carbonyl of the BChl-B850 (1651 and 1677 cm Ϫ1 ) and of the BChl-B800 (1701 cm Ϫ1 ) (9, 42, 43). The considerable downshift of one of the BChl-B850 13 1 keto bands to 1651 cm Ϫ1 has been proposed to reflect strong hydrogen bonding (42). More recently, this hydrogen bond has been assigned by site-directed mutagenesis to the hydroxy group of ␣-serine Ϫ4 and the 13 1 keto group of ␤-BChl-B850 (9).…”

Section: Fig 3 Optical Absorption and CD Spectra Of Wt Lh2 (-) Lh2mentioning

confidence: 99%

“…5). Previously, the serine at position Ϫ4 has been identified as the hydrogen-bonding partner to the C13 1 keto group of ␤-BChl-B850 in wt LH2 from R. sphaeroides by resonance Raman spectroscopy (9,42).…”

Section: Fig 3 Optical Absorption and CD Spectra Of Wt Lh2 (-) Lh2mentioning

confidence: 99%

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Hydrogen Bonding in a Model Bacteriochlorophyll-binding Site Drives Assembly of Light Harvesting Complex

Kwa¹,

García‐Martín²,

Végh

et al. 2004

Journal of Biological Chemistry

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In this study, the contribution of intramembrane hydrogen bonding at the interface between polypeptide and cofactor is explored in the native lipid environment by use of model bacteriochlorophyll proteins. In the peripheral antenna complex, LH2, large portions of the transmembrane helices, which make up the dimeric bacteriochlorophyll-binding site, are replaced by simplified, alternating alanine-leucine stretches. Replacement of either one of the two helices with the helices containing the model sequence at a time results in the assembly of complexes with nearly native light harvesting properties. In contrast, replacement of both helices results in the loss of antenna complexes from the membrane. The assembly of such doubly modified complexes is restored by a single intramembrane serine residue at position ؊4 relative to the liganding histidine of the ␣-subunit. In situ analysis of the spectral properties in a series of site-directed mutants reveals a critical dependence of the model complex assembly on the side chain of the residue at this position in the helix. A hydrogen bond between the hydroxy group of the serine and the 13 1 keto group of one of the central bacteriochlorophylls of the complexes is identified by Raman spectroscopy in the model antenna complex containing one of the alanine-leucine helices. The additional OH group of the serine residue, which participates in hydrogen bonding, increases the thermal stability of the model complexes in the native membrane. Intramembrane hydrogen bonding is thus shown to be a key factor for the binding of bacteriochlorophyll and assembly of this model cofactor-polypeptide site.

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Section: Fig 3 Optical Absorption and CD Spectra Of Wt Lh2 (-) Lh2supporting

confidence: 66%

Section: Fig 3 Optical Absorption and CD Spectra Of Wt Lh2 (-) Lh2mentioning

confidence: 99%

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Hydrogen Bonding in a Model Bacteriochlorophyll-binding Site Drives Assembly of Light Harvesting Complex

Kwa¹,

García‐Martín²,

Végh

et al. 2004

Journal of Biological Chemistry

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“…acidophila B800-850 and B800-820 confirm the absence of two hydrogen bonds to C 2 -acetyls in the latter species and their presence in the former complex. 18 The energy transfer characteristics of the mutants are similar to wild-type (WT) as is concluded from fluorescence excitation, 11 picosecond pump-probe measurements, 19 and holeburning spectroscopy. 20, 21 The energy transfer rate from B800 to B850 was even found to increase in the blue-shifted mutants 6 The sequences are aligned to their conserved histidine (H) given in bold characters, residues which ligate the 850 Bchl a molecules.…”

Section: Introductionmentioning

confidence: 54%

Characterization of the Light-Harvesting Antennas of Photosynthetic Purple Bacteria by Stark Spectroscopy. 2. LH2 Complexes: Influence of the Protein Environment

et al. 1997

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We have performed low-temperature Stark spectroscopy on a variety of different LH2 complexes from four photosynthetic bacteria, with the aim of characterizing the electric field response of the B800 and B850 absorption properties as a function of the protein environment. The following LH2 complexes were investigated: B800-850 and B800-820 of Rhodopseudomonas (Rps) acidophila; B800-850, B800-840 (RTyr +13 fPhe), and B800-826 (RTyr +13 fPhe, RTyr +14 fLeu) of Rhodobacter (Rb.) sphaeroides; B800-850 and B800-830 (obtained at high LDAO) of Ectothiorhodospira sp.; and B800-850 of Rhodospirillum (Rsp.) molischianum. For all these cases the spectral blue shift of B850 has been assigned to the loss hydrogenbonding interaction with the acetyl carbonyl of bacteriochlorophyll a. |∆µ| values for the 850 nm bands as well as for the blue-shifted bands are all on the order of 3-4.5 D/f. The loss of hydrogen-bonding interactions has only small effects on |∆µ| in these complexes. The values of the difference polarizability, Tr(∆r), are large (600-1400 Å 3 /f 2 ). The results are discussed in terms of crystal-structure-based models for LH2, in which pigment-pigment and pigment-protein interactions are considered; strong pigment-pigment interactions were found to be especially important. The values of |∆µ| for the 800 nm band are small, 1.0-1.5 D/f for LH2 complexes from Rb. sphaeroides and Rps. acidophila. However, in Rsp. molischianum and Ectothiorhodospira sp. |∆µ| values are much larger, of the order of 3 D/f. The difference in the B800 band is assigned to the difference in orientation of the B800 pigments in Rsp. molischianum and Ectothiorhodospira sp., as compared to the Rps. acidophila and Rb. sphaeroides. Due to the difference in orientation, the interactions of the Bchl a with the surrounding protein and neighboring carotenoid pigments are also not identical.

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“…The molecular origin of the spectral difference between B800-820 and B800-850 type LH2 is well understood. Hydrogen bonds between the α-and β-polypeptides and the C 2 -acetyl groups of the bacteriochlorophyll (23)(24)(25), or rotation of the C 2 -acetyl groups (26) are responsible for tuning the energy of the bacteriochlorophyll Q y transition moment.…”

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confidence: 99%

Antenna mixing in photosynthetic membranes from Phaeospirillum molischianum

Mascle-Allemand¹,

Duquesne²,

Lebrun

et al. 2010

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

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We have investigated the adaptation of the light-harvesting system of the photosynthetic bacterium Phaeospirillum molischianum (DSM120) to very low light conditions. This strain is able to respond to changing light conditions by differentially modulating the expression of a family of puc operons that encode for peripheral light-harvesting complex (LH2) polypeptides. This modulation can result in a complete shift between the production of LH2 complexes absorbing maximally near 850 nm to those absorbing near 820 nm. In contradiction to prevailing wisdom, analysis of the LH2 rings found in the photosynthetic membranes during light adaptation are shown to have intermediate spectral and electrostatic properties. By chemical cross-linking and mass-spectrometry we show that individual LH2 rings and subunits can contain a mixture of polypeptides derived from the different operons. These observations show that polypeptide synthesis and insertion into the membrane are not strongly coupled to LH2 assembly. We show that the light-harvesting complexes resulting from this mixing could be important in maintaining photosynthetic efficiency during adaptation.chromatic adaptation | membrane protein | photosynthetic bacteria | Rhodospirillum molischianum P hotosynthetic bacteria are able to efficiently convert incident light into chemical potential energy via a light-driven cyclic electron transfer pathway (1). This process depends on the efficient absorption of incident light energy and the transfer of this energy to the reaction center. Measurements of the quantum efficiency of the light-harvesting apparatus indicate that very little energy is lost during the migration of the exciton from the point of initial absorption to the reaction center (1). The light-harvesting system of many bacteria contains two different pigment-protein complexes. The core complex contains one or two reaction centers in close association with a light-harvesting system (LH1) and a smaller peripheral complex (LH2) that transfers the absorbed excitation energy to the core complex. Both types of light-harvesting complex, LH1 and LH2, are constructed from oligomers of a similar basic subunit containing 2 polypeptides (α and β) with associated bacteriochlorophyll and carotenoid pigments. Their structures are known from x-ray crystallography (2-4), electron crystallography (5), and more recently from atomic force microscopy (6-11).The LH2 complexes are circular oligomers of typically 9 αβ subunits (3), in which 18 long wavelength-absorbing bacteriochlorophyll molecules are sandwiched between the inner ring of α-polypeptides and an outer-ring of β-polypeptides. A second series of 9 bacteriochlorohpyll molecules, closer to the cytoplasmic membrane surface, occupies gaps between the β-polypeptides. This general architecture is slightly variable, with in particular the number of monomeric units forming the circular architecture depending on the species and environmental conditions (2,7,12,13). In the species studied in this work, Phaeospirillum (Ph.) molischianum...

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Structure and Properties of the Bacteriochlorophyll Binding Site in Peripheral Light-Harvesting Complexes of Purple Bacteria

Cited by 74 publications

References 20 publications

Hydrogen Bonding in a Model Bacteriochlorophyll-binding Site Drives Assembly of Light Harvesting Complex

Hydrogen Bonding in a Model Bacteriochlorophyll-binding Site Drives Assembly of Light Harvesting Complex

Characterization of the Light-Harvesting Antennas of Photosynthetic Purple Bacteria by Stark Spectroscopy. 2. LH2 Complexes: Influence of the Protein Environment

Antenna mixing in photosynthetic membranes from Phaeospirillum molischianum

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