Reconstitution of Light-Harvesting Complexes from Chlorella fusca (Chlorophyceae) and Mantoniella squamata (Prasinophyceae)

Meyer, Matthias; Wilhelm, Christian

doi:10.1515/znc-1993-5-611

Cited by 17 publications

(9 citation statements)

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“…Nonstoichiometric carotenoid contents could also be explained by the fact that a single pigment-protein species comprises several subpopulations with heterogeneous pigment composition. The higher lutein content found in r-LHCI-730 as compared with n-LHCI-730 may also be the result of variability in pigment binding such as has been reported previously for LHCII (42,43). Regardless of the reason of the nonstoichiometric carotenoid levels, the molar carotenoid͞Chl ratio of about 0.2 for LHCI-730 in the present study is in accordance with ratios calculated for different LHCIIs (44), although somewhat higher values have been obtained by others (41,45).…”

Section: Discussionmentioning

confidence: 51%

In vitro reconstitution of the photosystem I light-harvesting complex LHCI-730: Heterodimerization is required for antenna pigment organization

Schmid

Cammarata

Bruns

et al. 1997

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

156

186

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Here we describe the in vitro reconstitution of photosystem I light-harvesting complexes with pigments and proteins (Lhca1 and Lhca4) obtained by overexpression of tomato Lhca genes in Escherichia coli. Using Lhca1 and Lhca4 individually for reconstitution results in monomeric pigmentproteins, whereas a combination thereof yields a dimeric complex. Interactions of the apoproteins is highly specific, as reconstitution of either of the two constituent proteins in combination with a light-harvesting protein of photosystem II does not result in dimerization. The reconstituted Lhca1͞4, but not complexes obtained with either Lhca1 or Lhca4 alone, closely resembles the native LHCI-730 dimer from tomato leaves with regard to spectroscopic properties, pigment composition, and stoichiometry. Monomeric complexes of Lhca1 or Lhca4 possess lower pigment͞protein ratios, indicating that interactions of the two subunits not only facilitates pigment reorganization but also recruitment of additional pigments. In addition to higher averages of chlorophyll a͞b ratios in monomeric complexes than in LHCI-730, comparative f luorescence and CD spectra demonstrate that heterodimerization involves preferential ligation of more chlorophyll b.Precise assembly and alignment of pigments with the various proteins encoded by a family of nuclear Lhc genes underly the formation of the light-harvesting complexes (LHCs) of thylakoid membranes, enabling the collection of solar energy and its transmission to the two photochemically active reaction centers. Although the major LHCII has been analyzed in detail with respect to protein and pigment composition and organization (1), information about LHCs of photosystem I (PSI) are limited, mostly because they are difficult to isolate abundantly in an intact state. The original finding that four proteins of about 21 to 24 kDa form the LHCI (2) is now widely accepted, and the respective genes have been identified, cloned, and sequenced (3, 4). Recently, closely related photosystem I antenna components have been identified in red algae (5, 6). In vascular plants, there are two major LHCI subfractions with different protein compositions and fluorescence properties (7-9). One, LHCI-680, is enriched in polypeptides of 24 and 23 kDa (Lhca3 and Lhca2, respectively), has characteristic 77-K fluorescence at 680 nm and a low density in sucrose gradients, and is regarded as monomeric also on the basis of electrophoretic mobility. The LHCI-680 complex can be resolved into two green bands, one enriched in Lhca2 and the other in Lhca3, showing that both proteins are pigment binding (8, 10). The second complex, LHCI-730, exhibits 77-K fluorescence around 730 nm, has a higher sedimentation coefficient, is associated with proteins of 22 and 21 kDa (Lhca1 and Lhca4, respectively), and is considered to be dimeric (7-11). Further dissection of the LHCI-730 complex has not been achieved, leaving open the question of the extent to which both constitutent apoproteins function in pigment binding and whether the complex i...

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Section: Discussionmentioning

confidence: 51%

In vitro reconstitution of the photosystem I light-harvesting complex LHCI-730: Heterodimerization is required for antenna pigment organization

Schmid

Cammarata

Bruns

et al. 1997

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

156

186

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“…This was proposed for Chl binding by LHCI in barley (60), and results obtained with maize seedlings exposed to intermittent light also revealed flexibility in pigment binding in vivo (61). Additionally, reconstitution studies demonstrated the interchangeability of LHC proteins and carotenoids from alga and higher plants (21,62,63).…”

Section: Resultsmentioning

confidence: 78%

Pigment Binding of Photosystem I Light-harvesting Proteins

Schmid

Potthast

Wiener

et al. 2002

Journal of Biological Chemistry

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“…We conclude that the cooperative effect is not due to zeaxanthin binding to PsbS. (50), which includes many members from higher plants, green algae, red algae, and chromophyta (36,51). These proteins, with antenna function, cooperatively bind chlorophyll and xanthophyll chromophores, which are both needed for the assembly of pigmentprotein complexes in vivo and in vitro (32).…”

Section: Figure 9 Conformational Analysis Of Recombinant Psbs Refoldmentioning

confidence: 99%

Interactions between the Photosystem II Subunit PsbS and Xanthophylls Studied in Vivo and in Vitro

Bonente

Howes

Caffarri

et al. 2008

Journal of Biological Chemistry

128

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The photosystem II subunit PsbS is essential for excess energy dissipation (qE); however, both lutein and zeaxanthin are needed for its full activation. Based on previous work, two models can be proposed in which PsbS is either 1) the gene product where the quenching activity is located or 2) a proton-sensing trigger that activates the quencher molecules. The first hypothesis requires xanthophyll binding to two PsbS-binding sites, each activated by the protonation of a dicyclohexylcarbodiimide-binding lumen-exposed glutamic acid residue. To assess the existence and properties of these xanthophyll-binding sites, PsbS point mutants on each of the two Glu residues PsbS E122Q and PsbS E226Q were crossed with the npq1/npq4 and lut2/ npq4 mutants lacking zeaxanthin and lutein, respectively. Double mutants E122Q/npq1 and E226Q/npq1 had no qE, whereas E122Q/lut2 and E226Q/lut2 showed a strong qE reduction with respect to both lut2 and single glutamate mutants. These findings exclude a specific interaction between lutein or zeaxanthin and a dicyclohexylcarbodiimide-binding site and suggest that the dependence of nonphotochemical quenching on xanthophyll composition is not due to pigment binding to PsbS. To verify, in vitro, the capacity of xanthophylls to bind PsbS, we have produced recombinant PsbS refolded with purified pigments and shown that Raman signals, previously attributed to PsbS-zeaxanthin interactions, are in fact due to xanthophyll aggregation. We conclude that the xanthophyll dependence of qE is not due to PsbS but to other pigment-binding proteins, probably of the Lhcb type. Nonphotochemical quenching (NPQ)2 is a protective mechanism against overexcitation of photosystem II, consisting of heat dissipation of excess energy. This process, although present in all photosynthetic organisms, has been particularly studied in higher plants and green algae. Early work identified thylakoid lumen acidification as an essential factor for NPQ (1). Excess light increases proton pumping into the thylakoid lumen, which elicits chlorophyll fluorescence quenching dependent on protein protonation events. This is shown by the inhibitory effects of DCCD, a protein-modifying agent that covalently binds to protonatable residues in hydrophobic environments (2). It has been found that the photosystem II subunit PsbS, a DCCD-binding protein (3), is required for NPQ and, in particular, for its rapid and reversible component qE (4). In fact, the capacity for qE depends on the stoichiometric presence of PsbS polypeptide (5). Some insight into the importance of xanthophylls for the NPQ mechanism can be gained from the xanthophyll biosynthesis mutants found in NPQ-depleted plants. In the npq1 mutant, which is unable to convert violaxanthin into zeaxanthin upon lumen acidification, qE is reduced, whereas npq2, which constitutively accumulates zeaxanthin, has faster NPQ induction and slower relaxation kinetics (6). In the lut2 mutant, lacking lutein (7), and in the lut2/npq2 double mutant, which has zeaxanthin as the only xanthophyll (8, ...

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Reconstitution of Light-Harvesting Complexes from Chlorella fusca (Chlorophyceae) and Mantoniella squamata (Prasinophyceae)

Cited by 17 publications

References 0 publications

In vitro reconstitution of the photosystem I light-harvesting complex LHCI-730: Heterodimerization is required for antenna pigment organization

In vitro reconstitution of the photosystem I light-harvesting complex LHCI-730: Heterodimerization is required for antenna pigment organization

Pigment Binding of Photosystem I Light-harvesting Proteins

Interactions between the Photosystem II Subunit PsbS and Xanthophylls Studied in Vivo and in Vitro

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