Spectral alterations in Rhodobacter capsulatus mutants with site-directed changes in the bacteriochlorophyll-binding site of the B880 light-harvesting complex

Olivera, Leticia M.; Westerhuis, Willem H.J.; Niederman, Robert A.

doi:10.1016/0005-2728(94)90247-x

Cited by 5 publications

(3 citation statements)

References 42 publications

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“…To understand fully how these naturally occurring pigment–protein complexes harvest light so efficiently, it is necessary to employ spectroscopic tools that reveal directly the dynamics and efficiency of energy transfer and the nature of the excited energy states associated with the bound pigments. The spectroscopic studies are aided by the ability to make systematic alterations in the structures of the light-harvesting complexes, and then to examine how these changes manifest themselves in the spectroscopic observables, dynamics of energy transfer and efficiency of antenna function (Akahane et al 2004; Cammarata et al 1990; Chadwick et al 1987; Crielaard et al 1994; Croce et al 1999; Davidson and Cogdell 1981; Frank 1999; Fraser et al 1999; Morosinotto et al 2002; Olivera et al 1994; Olsen et al 1997; Plumley and Schmidt 1987; Remelli et al 1999; Struck and Scheer 1991; Struck et al 1992). …”

Section: Introductionmentioning

confidence: 99%

Optical spectroscopic studies of light-harvesting by pigment-reconstituted peridinin-chlorophyll-proteins at cryogenic temperatures

et al. 2006

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Low temperature, steady-state, optical spectroscopic methods were used to study the spectral features of peridinin-chlorophyll-protein (PCP) complexes in which recombinant apoprotein has been refolded in the presence of peridinin and either chlo-Absorption spectra taken at 10 K provide better resolution of the spectroscopic bands than seen at room temperature and reveal specific pigment-protein interactions responsible for the positions of the Q y bands of the chlorophylls. The study reveals that the functional groups attached to Ring I of the two protein-bound chlorophylls modulate the Q y and Soret transition energies. Fluorescence excitation spectra were used to compute energy transfer efficiencies of the various complexes at room temperature and these were correlated with previously reported ultrafast, time-resolved optical spectroscopic dynamics data. The results illustrate the robust nature and value of the PCP complex, which maintains a high efficiency of antenna function even in the presence of non-native chlorophyll species, as an effective tool for elucidating the molecular details of photosynthetic light-harvesting.

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Section: Introductionmentioning

confidence: 99%

Optical spectroscopic studies of light-harvesting by pigment-reconstituted peridinin-chlorophyll-proteins at cryogenic temperatures

et al. 2006

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“…Recent mutagenesis experiments on LH1 polypeptides have illustrated the importance of certain amino acids or specific regions of the polypeptides for LH1 assembly and formation in vivo (Bylina et al, 1988;Dorge et al, 1990;Stiehle et al, 1990;Babst et al, 1991;Richter et al, 1991Richter et al, , 1992Olivera et al, 1994). Also, mutations of selected highly conserved residues and the attending spectral changes of the LH1 and/or the peripheral LH (LH2) have been used to provide insight into those amino acids that may be proximal to and interacting with the BChl (Babst et al, 1991;Fowler et al, 1992Fowler et al, , 1993Crielaard et al, 1994;Olivera et al, 1994;Olsen et al, 1994;Visschers et al, 1994). The in vitro reconstitution assay complements the mutagenesis studies and offers distinct advantages for structure-function studies, since it relies solely upon the interactions between the a-and /3-polypeptides and BChl within a detergent milieu.…”

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confidence: 99%

Enzymic and chemical cleavage of the core light-harvesting polypeptides of photosynthetic bacteria: Determination of the minimal polypeptide size and structure required for subunit and light-harvesting complex formation

Meadows¹,

Iida²,

Tsuda³

et al. 1995

Biochemistry

135

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To ascertain the minimal structural requirements for formation of the subunit and core light-harvesting complex (LH1), the alpha- and beta-polypeptides of the LH1 from three purple photosynthetic bacteria were enzymatically or chemically truncated or modified. These polypeptides were then used in reconstitution experiments with bacteriochlorophyll a (BChla), and the formation of subunit and LH1 complexes was evaluated using absorbance and circular dichroism spectroscopies. Truncation or modification outside of the conserved core sequence region of the polypeptides had no effect on subunit or LH1 formation. However, the extent of formation and stability of the subunit and LH1 decreased as the polypeptide was shortened inside the core region within the N-terminal domain. This behavior was suggested to be due to the loss of potential ion-pairing and/or hydrogen-bonding interactions between the polypeptides. While the spectroscopic properties of the subunit complexes generated using truncated polypeptides were analogous to those obtained using native polypeptides, in some cases the resulting LH1 complex absorption was blue-shifted relative to the control. Thus, truncation within the N-terminal domain may have long-range effects on the immediate BChla binding environment, since the putative BChla binding site resides near the C-terminal end of the polypeptides. It was also demonstrated that the His located within the membrane-spanning domain on the N-terminal end of the beta-polypeptide is not participating in ligation of the BChla in the reconstituted subunit and therefore probably not in LH1.

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“…Prior to elucidation of the LH2 crystal structure, pigmentprotein interactions had been identified by site-directed mutagenesis of amino acid residues in both the LH1 (8)(9)(10)(11) and LH2 complexes (12)(13)(14)(15). However, alteration of one, or at most two residues at a time, samples protein sequence space insufficiently to permit the isolation of many mutants with highly interesting and informative phenotypes.…”

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confidence: 99%

Hydrogen Bonding and Circular Dichroism of Bacteriochlorophylls in the Rhodobacter capsulatus Light-Harvesting 2 Complex Altered by Combinatorial Mutagenesis

Sturgis

Robert

et al. 1998

Biochemistry

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We have investigated the spectroscopic properties of two classes of light-harvesting 2 (LH2, B800-850) mutants of Rhodobacter capsulatus obtained by combinatorial mutagenesis to the C-terminal half of the beta-apoprotein: a pseudoLH2 (pLH2) class, in which the 800-nm absorption was normal but the 850-nm peak was blue-shifted by up to 14 nm, and the other a pseudoLH1 (pLH1) class, which lacked the 800-nm absorption band and showed 850-nm absorption red-shifts of up to 30 nm. In several of the pLH1 antennae, carotenoid depletion contributed to the phenotype, while in the pLH2 complexes there was some carotenoid enrichment. A number of mutants from each class have also been characterized by low-temperature absorption and fluorescence spectroscopy, resonance Raman spectroscopy, and circular dichroism. In all of the mutants investigated, the B850 bacteriochlorophyll a binding site remained intact, conserving both the hydrogen bonding environment of the chromophores and their conformation and liganding. In contrast, the intensity of the CD spectra of pLH1 complexes was considerably reduced, relative to that of wild-type or pLH2 complexes, consistent with alterations in the interactions between pigments and in their relative orientation. Elevated fluorescence polarization over the red wing of the B850 band in the pLH2 complexes indicated a reduction of exciton mobility within the ring of BChl molecules. Possible structural alterations governing the spectral properties of the different mutants are discussed.

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Spectral alterations in Rhodobacter capsulatus mutants with site-directed changes in the bacteriochlorophyll-binding site of the B880 light-harvesting complex

Cited by 5 publications

References 42 publications

Optical spectroscopic studies of light-harvesting by pigment-reconstituted peridinin-chlorophyll-proteins at cryogenic temperatures

Optical spectroscopic studies of light-harvesting by pigment-reconstituted peridinin-chlorophyll-proteins at cryogenic temperatures

Enzymic and chemical cleavage of the core light-harvesting polypeptides of photosynthetic bacteria: Determination of the minimal polypeptide size and structure required for subunit and light-harvesting complex formation

Hydrogen Bonding and Circular Dichroism of Bacteriochlorophylls in the Rhodobacter capsulatus Light-Harvesting 2 Complex Altered by Combinatorial Mutagenesis

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