Probing the binding sites of exchanged chlorophyll <i>a</i> in LH2 by Raman and site‐selection fluorescence spectroscopies

Gall, Andrew; Robert, Bruno; Cogdell, Richard J.; Bellissent-Funel, Marie-Claire; Fraser, Niall J.

doi:10.1016/s0014-5793(01)02161-5

Cited by 18 publications

(12 citation statements)

References 30 publications

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“…The recovery of the peak positions of rhodopin glucoside by reconstitution of 3‐acetyl Chl a into B800‐free LH2 suggests that 3‐acetyl Chl a is accommodated in the B800‐binding pockets in the same manner as BChl a . This is supported by previous resonance Raman spectroscopy of LH2 proteins whose B800‐binding sites are occupied with exogenous BChl a and Chl a . In contrast, rhodopin glucoside in AcPChl‐reconstituted LH2 had its absorption bands at 521 and 486 nm.…”

Section: Resultssupporting

confidence: 75%

Characterization of 3‐Acetyl Chlorophyll a and 3‐Acetyl Protochlorophyll a Accommodated in the B800 Binding Sites of Photosynthetic Light‐Harvesting Complex 2 in the Purple Photosynthetic Bacterium Rhodoblastus acidophilus

Saga

Miyagi

2018

Photochem & Photobiology

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We present the detailed characterization on the reconstitution of two cyclic tetrapyrrole pigments that have the same substituents but differ in the degree of hydrogenation in the macrocycles from bacteriochlorophyll (BChl) a (7,8,17,18-tetrahydroporphyrin) into the binding sites of B800 BChl a in light-harvesting complex 2 (LH2) of purple photosynthetic bacteria. Both 3-acetyl chlorophyll (Chl) a (17,18-dihydroporphyrin) and 3-acetyl protochlorophyll (PChl) a (porphyrin) were inserted into the B800-binding pockets in LH2, indicating that these pockets allow alteration of the degree of hydrogenation in the cyclic tetrapyrroles. Redshifts of the Q peak positions of 3-acetyl (P)Chl a by insertion into the B800-binding sites were smaller than that of BChl a. The relative Q absorbance of 3-acetyl (P)Chl a to B850 BChl a in the reconstituted proteins was significantly smaller than that of B800 BChl a in native LH2 in spite of their high occupancy in the B800-binding sites. These are ascribable to the smaller dipole strengths of 3-acetyl (P)Chl a. We also performed the coreconstitution of both 3-acetyl Chl a and BChl a into the nine B800-binding sites in LH2, indicating that the affinity of 3-acetyl Chl a to the B800-cavity was slightly higher than that of BChl a.

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Section: Resultssupporting

confidence: 75%

Characterization of 3‐Acetyl Chlorophyll a and 3‐Acetyl Protochlorophyll a Accommodated in the B800 Binding Sites of Photosynthetic Light‐Harvesting Complex 2 in the Purple Photosynthetic Bacterium Rhodoblastus acidophilus

Saga

Miyagi

2018

Photochem & Photobiology

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“…In that case, the upper excitonic levels of B850 band, lying in the vicinity of the B800 band, might play a role in the relaxation dynamics under the excitation near 800 nm [30,31]. Moreover, by using the different B800-released LH2 complexes, the characteristics of upper excitonic levels of B850 band have been directly observed by circular dichroism spectra, nonlinear absorption and ultrafast pump-probe techniques [32,33]. Figure 5 shows the absorption spectrum of B850p.…”

Section: Energy Transfer Within the Lh2 Complexmentioning

confidence: 99%

“…It is considered that al- though the deletion of B800 pigments results in a small red shift of B850 band in B850 p, the coupling of the B850 pigments in the ring is not significantly affected [29]. In that case, in the range between 820 nm and 850 nm, the fs dynamics of two kinds of LH2 complexes would be similar, mainly reflecting the effect of B850 pigments [30,33].…”

Section: Energy Transfer Within the Lh2 Complexmentioning

confidence: 99%

The study of photo-induced ultrafast dynamics in light-harvesting complex LH2 of purple bacteria

et al. 2006

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In this paper, we introduce the photo-induced ultrafast dynamics taking place in the peripheral light harvesting antenna LH2 from purple bacteria Rhodobacter sphaeroides by using absorption, fluorescence emission and ultrafast spectroscopic techniques. Three kinds of LH2 samples, pH treated LH2 (complete removal of B800 pigments), carotenoid mutated LH2 (GM 309) and electrochemical oxidation treated LH2 were used in comparison with native LH2 to investigate the mechanism of photo-induced ultrafast energy transfer within the LH2 complex.

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“…By chemical treatment, the B800 BChl a can be removed and replaced with alternatives [ [48] , [49] , [50] , [51] , [52] , [53] , [54] ]. Promisingly, Chl a has been shown to bind correctly [ 55 ] and experiences a similar microenvironment to the native BChl a [ 15 ]. Reconstituted (B)Chls efficiently absorb light and transfer energy to the native B850 BChl a , even if there is little or no spectral overlap between them [ 49 , 50 , 56 ].…”

Section: Introductionmentioning

confidence: 99%

Engineering of B800 bacteriochlorophyll binding site specificity in the Rhodobacter sphaeroides LH2 antenna

Swainsbury

Faries

Niedzwiedzki

et al. 2019

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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The light-harvesting 2 complex (LH2) of the purple phototrophic bacterium Rhodobacter sphaeroides is a highly efficient, light-harvesting antenna that allows growth under a wide-range of light intensities. In order to expand the spectral range of this antenna complex, we first used a series of competition assays to measure the capacity of the non-native pigments 3-acetyl chlorophyll (Chl) a , Chl d , Chl f or bacteriochlorophyll (BChl) b to replace native BChl a in the B800 binding site of LH2. We then adjusted the B800 site and systematically assessed the binding of non-native pigments. We find that Arg −10 of the LH2 β polypeptide plays a crucial role in binding specificity, by providing a hydrogen-bond to the 3-acetyl group of native and non-native pigments. Reconstituted LH2 complexes harbouring the series of (B)Chls were examined by transient absorption and steady-state fluorescence spectroscopies. Although slowed 10-fold to ~6 ps, energy transfer from Chl a to B850 BChl a remained highly efficient. We measured faster energy-transfer time constants for Chl d (3.5 ps) and Chl f (2.7 ps), which have red-shifted absorption maxima compared to Chl a . BChl b , red-shifted from the native BChl a , gave extremely rapid (≤0.1 ps) transfer. These results show that modified LH2 complexes, combined with engineered (B)Chl biosynthesis pathways in vivo , have potential for retaining high efficiency whilst acquiring increased spectral range.

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Probing the binding sites of exchanged chlorophyll a in LH2 by Raman and site‐selection fluorescence spectroscopies

Cited by 18 publications

References 30 publications

Characterization of 3‐Acetyl Chlorophyll a and 3‐Acetyl Protochlorophyll a Accommodated in the B800 Binding Sites of Photosynthetic Light‐Harvesting Complex 2 in the Purple Photosynthetic Bacterium Rhodoblastus acidophilus

Characterization of 3‐Acetyl Chlorophyll a and 3‐Acetyl Protochlorophyll a Accommodated in the B800 Binding Sites of Photosynthetic Light‐Harvesting Complex 2 in the Purple Photosynthetic Bacterium Rhodoblastus acidophilus

The study of photo-induced ultrafast dynamics in light-harvesting complex LH2 of purple bacteria

Engineering of B800 bacteriochlorophyll binding site specificity in the Rhodobacter sphaeroides LH2 antenna

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