Distribution of the chlorophyll spectral forms in the chlorophyll-protein complexes of photosystem II antenna

Jennings, Robert C.; Bassi, Roberto; Garlaschi, Flavio M.; Dainese, Paola; Zucchelli, Giuseppe

doi:10.1021/bi00064a002

Cited by 105 publications

(104 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consistently, the half-time of this quenching component was found to be of ;2 min, thus longer than that of qE but much shorter than the time required for full V-to-Z conversion (Demmig-Adams et al, 1989). This is likely to be due to energy equilibration within the PSII antenna, which is energetically shaped as a shallow funnel (Jennings et al, 1993). The ultrafast chlorophyll-chlorophyll energy transfer between LHC protein subunits (Gradinaru et al, 1998) would extend the effect of a limited number of quenching centers within the pigment bed to the overall PSII.…”

Section: Relevance Of Zeaxanthin-induced Ph-independent Quenching Inmentioning

confidence: 99%

A Mechanism of Nonphotochemical Energy Dissipation, Independent from PsbS, Revealed by a Conformational Change in the Antenna Protein CP26

2005

Self Cite

View full text Add to dashboard Cite

The regulation of light harvesting in higher plant photosynthesis, defined as stress-dependent modulation of the ratio of energy transfer to the reaction centers versus heat dissipation, was studied by means of carotenoid biosynthesis mutants and recombinant light harvesting complexes (LHCs) with modified chromophore binding. The npq2 mutant of Arabidopsis thaliana, blocked in the biosynthesis of violaxanthin and thus accumulating zeaxanthin, was shown to have a lower fluorescence yield of chlorophyll in vivo and, correspondingly, a higher level of energy dissipation, with respect to the wildtype strain and npq1 mutant, the latter of which is incapable of zeaxanthin accumulation. Experiments on purified thylakoid membranes from all three mutants showed that the major source of the difference between the npq2 and wild-type preparations was a change in pigment to protein interactions, which can explain the lower chlorophyll fluorescence yield in the npq2 samples. Analysis of the xanthophyll binding LHC proteins showed that the Lhcb5 photosystem II subunit (also called CP26) undergoes a change in its pI upon binding of zeaxanthin. The same effect was observed in wild-type CP26 upon treatment that leads to the accumulation of zeaxanthin in the membrane and was interpreted as the consequence of a conformational change. This hypothesis was confirmed by the analysis of two recombinant proteins obtained by overexpression of the Lhcb5 apoprotein in Escherichia coli and reconstitution in vitro with either violaxanthin or zeaxanthin. The V and Z containing pigment-protein complexes obtained by this procedure showed different pIs and high and low fluorescence yields, respectively. These results confirm that LHC proteins exist in multiple conformations, an idea suggested by previous spectroscopic measurements ( Moya et al., 2001), and imply that the switch between the different LHC protein conformations is activated by the binding of zeaxanthin to the allosteric site L2. The results suggest that the quenching process induced by the accumulation of zeaxanthin contributes to qI, a component of NPQ whose origin was previously poorly understood.

show abstract

Section: Relevance Of Zeaxanthin-induced Ph-independent Quenching Inmentioning

confidence: 99%

A Mechanism of Nonphotochemical Energy Dissipation, Independent from PsbS, Revealed by a Conformational Change in the Antenna Protein CP26

2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…The most dramatic effect is an increase in the Chl b 652 nm absorption when the neoxanthin site is occupied. Among Lhc proteins, the prominent 652 nm peak is a unique feature of LHCII, whereas other members of the family exhibit a monotonic increase in absorption from 600 nm to the Chl a peak (35) even when the molar ratio between Chl b and Chl a is higher than in LHCII, as is the case in CP24 (19). This is likely to be due to the presence of only two carotenoid sites in Lhcb proteins other than Lhcb1-3 (36, 37) and therefore to the lack of the N1 site.…”

Section: Chlorophyll-carotenoid Interactions Explain the Characteristmentioning

confidence: 99%

Carotenoid-binding Sites of the Major Light-harvesting Complex II of Higher Plants

Croce

Weiß

Bassi

1999

Journal of Biological Chemistry

Self Cite

237

273

View full text Add to dashboard Cite

Recombinant light-harvesting complex II (LHCII) proteins with modified carotenoid composition have been obtained by in vitro reconstitution of the Lhcb1 protein overexpressed in bacteria. The monomeric protein possesses three xanthophyll-binding sites. The L1 and L2 sites, localized by electron crystallography in the helix A/helix B cross, have the highest affinity for lutein, but also bind violaxanthin and zeaxanthin with lower affinity. The latter xanthophyll causes disruption of excitation energy transfer. The occupancy of at least one of these sites, probably L1, is essential for protein folding. Neoxanthin is bound to a distinct site (N1) that is highly selective for this species and whose occupancy is not essential for protein folding. Whereas xanthophylls in the L1 and L2 sites interact mainly with chlorophyll a, neoxanthin shows strong interaction with chlorophyll b, inducing the hyperchromic effect of the 652 nm absorption band. This observation explains the recent results of energy transfer from carotenoids to chlorophyll b obtained by femtosecond absorption spectroscopy. Whereas xanthophylls in the L1 and L2 sites are active in photoprotection through chlorophyll-triplet quenching, neoxanthin seems to act mainly in 1 O 2 * scavenging.Light energy for the photosynthesis of green plants is collected by an antenna system composed of many homologous proteins belonging to the Lhc multigene family (1). These pigment-protein complexes are organized around photosynthetic reaction centers to form supramolecular complexes embedded into the thylakoid membrane, accounting for ϳ70% of the pigment involved in plant photosynthesis. LHCII 1 is the most abundant light-harvesting complex in higher plants. The structure of this complex has been resolved at 3.4 Å by electron microscopy (2) and is formed by three hydrophobic transmembrane helices connected by hydrophilic loops and an amphipathic helix exposed to the luminal surface of the membrane. LHCII coordinates 7 Chl a, 5 Chl b, and 3-4 carotenoid molecules (lutein, neoxanthin, and a substoichiometric amount of violaxanthin) depending on the genotype (3) and the physiological state of the plant (4). In the structural model of LHCII (2), 2 xanthophyll molecules have been located in the center of the complex, forming an internal cross-brace interacting with helices A and B. These appear to be crucial for protein stabilization, as suggested by the fact that a stable LHCII complex cannot be obtained without lutein in refolding experiments (5, 6). Although the 2 central molecules were tentatively assigned to lutein (2), the structural resolution is insufficient for their identification and for the location of the xanthophyll molecule with respect to the 2 detected by structural analysis. The nature and location of the binding site for the third xanthophyll molecule are presently unknown. It is also unclear if the individual binding sites have different affinities for the three xanthophyll species.Carotenoids have at least five different roles in photosynthesis: 1) light h...

show abstract

“…Thus, an indirect involvement of RNA in the production and/or liberation of the plastid factor seems to be more likely. Because tRNAG'" is involved in driving tetrapyrrole synthesis (see below), it has been proposed that a pigment intermediate in the C, pathway could accomplish the function of the plastid factor (Johanningmeier and Howell, 1984).…”

Section: Morphological Cellular and Molecular Events During The Ligmentioning

confidence: 99%

“…Pioneering studies of Johanningmeier and Howell (1984) suggested that intermediates in the C, pathway, such as protoporphyrin IX, Mg"-protoporphyrin IX monomethyl ester, or Pchlide could be the signals that inhibit cab (Ihcb) mRNA accumulation in the dark. In the light, due to rapid consumption of the pigments during chlorophyll synthesis, the block of Ihcdb gene expression would be relieved, and the lhcah mRNAs could accumulate.…”

Section: Regulation Of Por Gene Expression Two Distinct Por Genesmentioning

confidence: 99%

“…In the light, due to rapid consumption of the pigments during chlorophyll synthesis, the block of Ihcdb gene expression would be relieved, and the lhcah mRNAs could accumulate. Johanningmeier and Howell (1984) further proposed that the plastid envelope might be the site from which these pigments are released to the cytosol. The identification of most of the aforementioned pigments and of many of the enzymes necessary for converting protoporphyrinogen IX to Pchlide in isolated envelope membranes of spinach chloroplasts seems to confirm this proposal.…”

Section: Regulation Of Por Gene Expression Two Distinct Por Genesmentioning

confidence: 99%

See 1 more Smart Citation

The Regulation of Enzymes Involved in Chlorophyll Biosynthesis

Reinbothe

1996

European Journal of Biochemistry

126

View full text Add to dashboard Cite

All living organisms contain tetrapyrroles. In plants, chlorophyll (chlorophyll a plus chlorophyll b) is the most abundant and probably most important tetrapyrrole. It is involved in light absorption and energy transduction during photosynthesis. Chlorophyll is synthesized from the intact carbon skeleton of glutamate via the C, pathway. This pathway takes place in the chloroplast. It is the aim of this review to summarize the current knowledge on the biochemistry and molecular biology of the C,-pathway enzymes, their regulated expression in response to light, and the impact of chlorophyll biosynthesis on chloroplast development. Particular emphasis will be placed on the key regulatory steps of chlorophyll biosynthesis in higher plants, such as 5-aminolevulinic acid formation, the production of Mg*+-protoporphyrin IX, and light-dependent protochlorophyllide reduction.

show abstract

Distribution of the chlorophyll spectral forms in the chlorophyll-protein complexes of photosystem II antenna

Cited by 105 publications

References 42 publications

A Mechanism of Nonphotochemical Energy Dissipation, Independent from PsbS, Revealed by a Conformational Change in the Antenna Protein CP26

A Mechanism of Nonphotochemical Energy Dissipation, Independent from PsbS, Revealed by a Conformational Change in the Antenna Protein CP26

Carotenoid-binding Sites of the Major Light-harvesting Complex II of Higher Plants

The Regulation of Enzymes Involved in Chlorophyll Biosynthesis

Contact Info

Product

Resources

About