Pigment Binding of Photosystem I Light-harvesting Proteins

Schmid, Volkmar; Potthast, Susanne; Wiener, Michaela; Bergauer, Verena; Paulsen, Harald; Storf, Stefanie

doi:10.1074/jbc.m205889200

Cited by 73 publications

(112 citation statements)

References 71 publications

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“…Obviously, interaction of Lhca proteins with PSI core proteins plays a major role in determining the interaction properties of some Lhca proteins. This could be in line with the finding that the Lhca2/a3 heterodimer present in native LHCI has not been successfully reconstituted from the individual Lhca proteins, yet [17]. The elevated amounts of Lhca5 in the Da1 line presumably are also partly present as homodimers in the Lhca1/a4 binding sites not occupied by Lhca1/a4 heterodimers.…”

Section: Resultssupporting

confidence: 77%

Lhca5 interaction with plant photosystem I

Luciński¹,

Schmid²,

Jansson³

et al. 2006

FEBS Letters

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In the outer antenna (LHCI) of higher plant photosystem I (PSI) four abundantly expressed light-harvesting protein of photosystem I (Lhca)-type proteins are organized in two heterodimeric domains (Lhca1/Lhca4 and Lhca2/Lhca3). Our cross-linking studies on PSI-LHCI preparations from wildtype Arabidopsis and pea plants indicate an exclusive interaction of the rarely expressed Lhca5 light-harvesting protein with LHCI in the Lhca2/Lhca3-site. In PSI particles with an altered LHCI composition Lhca5 assembles in the Lhca1/Lhca4 site, partly as a homodimer. This flexibility indicates a binding-competitive model for the LHCI assembly in plants regulated by molecular interactions of the Lhca proteins with the PSI core.

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Section: Resultssupporting

confidence: 77%

Lhca5 interaction with plant photosystem I

Luciński¹,

Schmid²,

Jansson³

et al. 2006

FEBS Letters

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“…The close relation between Lhca2 and Lhca4 is confirmed by sequence analysis, which shows 55% identity and 75% homology (14). Surprisingly, the distribution of red forms does not fit into the picture, because these are associated mainly with Lhca3 and Lhca4 (fluorescence emission at 725-730 nm), whereas Lhca1 and Lhca2 have emission at higher energy (702 nm) (12,13,15). Based on high homology between proteins with different content in red forms, a sequence motif associated with the presence of lowest absorption band, common to Lhca3 and Lhca4 and not present in Lhca1 and Lhca2, should possibly be detected.…”

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confidence: 68%

“…To test the hypothesis that this feature is also sufficient for the presence of this spectroscopic property, Lhca1 and Lhca2, which have His ligand at their A5 site (H47 and H52, respectively) and show emission at 702 nm (13), were mutated to Asn-47 and Asn-52. Both mutant proteins yielded a refolded monomeric product.…”

Section: Resultsmentioning

confidence: 99%

“…The first two have higher Chl b content with respect to Lhca1 and Lhca3 and bind two carotenoid molecules per polypeptide rather than three (12). For their folding, Lhca2 and Lhca4 require both Chl a and Chl b, whereas Lhca1 and Lhca3 are stable with Chl a only (12,13). Circular dichroism spectra, yielding information of pigment organization within the complex, also show strong similarities between Lhca2 and Lhca4 on one hand and Lhca3 and Lhca1 on the other (12).…”

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confidence: 88%

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The Nature of a Chlorophyll Ligand in Lhca Proteins Determines the Far Red Fluorescence Emission Typical of Photosystem I

Morosinotto

Breton

Bassi

et al. 2003

Journal of Biological Chemistry

173

220

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Photosystem I of higher plants is characterized by a typically long wavelength fluorescence emission associated to its light-harvesting complex I moiety. The origin of these low energy chlorophyll spectral forms was investigated by using site-directed mutagenesis of Lhca1-4 genes and in vitro reconstitution into recombinant pigment-protein complexes. We showed that the red-shifted absorption originates from chlorophyll-chlorophyll (Chl) excitonic interactions involving Chl A5 in each of the four Lhca antenna complexes. An essential requirement for the presence of the red-shifted absorption/fluorescence spectral forms was the presence of asparagine as a ligand for the Chl a chromophore in the binding site A5 of Lhca complexes. In Lhca3 and Lhca4, which exhibit the most red-shifted red forms, its substitution by histidine maintains the pigment binding and, yet, the red spectral forms are abolished. Conversely, in Lhca1, having very low amplitude of red forms, the substitution of Asn for His produces a red shift of the fluorescence emission, thus confirming that the nature of the Chl A5 ligand determines the correct organization of chromophores leading to the excitonic interaction responsible for the red-most forms. The red-shifted fluorescence emission at 730 nm is here proposed to originate from an absorption band at ϳ700 nm, which represents the low energy contribution of an excitonic interaction having the high energy band at 683 nm. Because the mutation does not affect Chl A5 orientation, we suggest that coordination by Asn of Chl A5 holds it at the correct distance with Chl B5.Photosystem I is a multisubunit pigment-protein complex of the chloroplast membrane acting as a plastocyanin/ferredoxin oxido-reductase in oxygenic photosynthesis. One important spectroscopic feature of PSI 1 is the presence of Chls absorbing at energy lower than the PSI primary electron donor, P700.Although these spectral forms account for only a small percentage of the total absorption, their effect in the energy transfer and trapping of PSI is very prominent (1), with at least 80% of excitation in the complex transiting through them on their way to P700 (2). It has been widely proposed that these forms represent the low energy contributions of excitonic interactions, which involve two or more Chl molecules (3-5); however, the identity of the chromophores involved and the details of the interaction are still unknown.Although the presence of low energy-absorbing Chls is ubiquitous in the PSI of different organisms, their amounts and energies appear to be highly species-dependent (1). In the PSI of higher plants, the red forms are associated with the outer antenna, LHCI (6, 7). LHCI is composed by four pigmentbinding proteins, namely Lhca1-4 (6, 8). These complexes, localized on one side of the core complex (9, 10), are organized in dimers with 10 Chl molecules per subunit (11).As for their properties, Lhca2 and Lhca4 differ from Lhca1 and Lhca3 in many respects. The first two have higher Chl b content with respect to Lhca1 and Lhca3 an...

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“…As in the PSI core antenna, excitonically coupled dimers or trimers of Chl a or Chl b in the LHCI were suggested to form a pool of red pigments in the LHCI (9 -11). Recent experiments with antisense inhibited Arabidopsis plants in vivo (12), and reconstitution of the polypeptides in vitro (13,14) suggests that the presence of low energy pigments is a feature of all four Lhca polypeptides (Lhca1, Lhca2, Lhca3, and Lhca4). Lhca1 seems to possess the less red-shifted spectral forms (684 nm) (14, 15), which is in agreement with its close relatedness to a minor lightharvesting polypeptide of PSII, CP29.…”

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confidence: 99%

Structural Modeling of the Lhca4 Subunit of LHCI-730 Peripheral Antenna in Photosystem I Based on Similarity with LHCII

Melkozernov

Blankenship

2003

Journal of Biological Chemistry

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Peripheral chlorophyll a/b binding antenna of photosystem I (LHCI) from green algae and higher plants binds specific low energy absorbing chlorophylls (red pigments) that give rise to a unique red-shifted emission. A three-dimensional structural model of the Lhca4 polypeptide from the LHCI from higher plants was constructed on the basis of comparative sequence analysis, secondary structure prediction, and homology modeling using LHCII as a template. The obtained model of Lhca4 helps to visualize protein ligands to nine chlorophylls (Chls) and three potential His residues to extra Chls. Central domain of the Lhca4 comprising the first (A) and the third (C) transmembrane (TM) helices that binds 6 Chl molecules and two carotenoids is conserved structurally, whereas the interface between the first and the second TM helices and the outer surface of the second TM helix differ significantly among the LHCI and LHCII polypeptides. The model of Lhca4 predicts a histidine residue in the second TM helix, a potential binding site for extra Chl in close proximity to Chls a5 and b5 (labeling by Kü hlbrandt). The interpigment interactions in the formed pigment cluster are suggested to cause a red spectral shift in absorption and emission. Modeling of the LHCI-730 heterodimer based on the model structures of Lhca1 and Lhca4 allowed us to suggest potential sites of pigment-pigment interactions that might be formed upon heterodimerization or docking of the LHCI dimers to the surface of PSI.In photosynthetic apparatus of green algae and higher plants the peripheral chlorophyll a/b binding antenna (LHC) 1 increases the light-harvesting capacities of Chl a binding photosystem (PS) core reaction centers I and II (1). In adaptive response to changing environmental conditions, the peripheral antennas undergo dynamic structural changes resulting in regulation of excitation flows between the two photosystems and a photoprotection against excess illumination (2, 3).In contrast to the PSII-LHCII supercomplex that serves water oxidation function, the PSI-LHCI supercomplex ensures stable supply of reducing equivalents for CO 2 fixation in algae and green plants (1). The PSI supercomplex operates at lower energies than PSII. This is determined by energetics of electron transfer reactions in thylakoids, by low energy absorption of the primary electron donor P700 at 700 nm, as well as by an increase in absorption cross-section of the PSI holocomplex due to low energy absorbing Chls both in the PSI core and in LHCI antenna (4). Due to these low energy absorbing Chls, both PSI core and PSI-LHCI fluoresce at 720 -740 nm, a feature that is widely used for functional identification of PSI. X-ray crystallography of the PSI core from cyanobacteria (5) as well as modeling studies (6 -8) indicates strong interpigment interactions and unique protein environment as a source for the low energy shifts in absorption of PSI. Biochemical and spectroscopic studies of LHCI suggest that in the PSI-LHCI supercomplexes the peripheral antenna and the PSI core antenna...

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Pigment Binding of Photosystem I Light-harvesting Proteins

Cited by 73 publications

References 71 publications

Lhca5 interaction with plant photosystem I

Lhca5 interaction with plant photosystem I

The Nature of a Chlorophyll Ligand in Lhca Proteins Determines the Far Red Fluorescence Emission Typical of Photosystem I

Structural Modeling of the Lhca4 Subunit of LHCI-730 Peripheral Antenna in Photosystem I Based on Similarity with LHCII

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