Spectroscopic properties of LHC-II, the main light-harvesting chlorophyll a/b protein complex from chloroplast membranes

Hemelrijk, Petra W.; Kwa, Stefan L.S.; Grondelle, Rienk van; Dekker, Jan

doi:10.1016/s0005-2728(05)80331-7

Cited by 169 publications

(188 citation statements)

References 46 publications

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“…Our Lhcb3 preparation seems to bind somewhat less Chl b than Lhcb1 and Lhcb2 (a factor of 0.14 times less) when comparing integrated areas at 640-660 nm after normalization of the Chl a absorption intensity at 660-710 nm. The positions of all the absorption subbands (see Figure 2b) are very close to those of the native complexes, both monomers and trimers (see also Hemelrijk et al 1992;Nussberger et al 1994;van Amerongen et al 1994;Ruban et al 1997;Palacios et al 2003), and are very similar for the different isoforms, suggesting a similar pigment organization in the complexes. Only small shifts are observed.…”

Section: Absorption Ld Spectra and Time-resolved Fluorescencementioning

confidence: 55%

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

et al. 2006

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In this article we report the characterization of the energy transfer process in the reconstituted isoforms of the plant light-harvesting complex II. Homotrimers of recombinant Lhcb1 and Lhcb2 and monomers of Lhcb3 were compared to native trimeric complexes. We used low-intensity femtosecond transient absorption (TA) and time-resolved fluorescence measurements at 77 K and at room temperature, respectively, to excite the complexes selectively in the chlorophyll b absorption band at 650 nm with 80 fs pulses and on the high-energy side of the chlorophyll a absorption band at 662 nm with 180 fs pulses. The subsequent kinetics was probed at 30-35 different wavelengths in the region from 635 to 700 nm. The rate constants for energy transfer were very similar, indicating that structurally the three isoforms are highly homologous and that probably none of them play a more significant role in light-harvesting and energy transfer. No signature has been found in the transient absorption measurements at 77 K for Lhcb3 which might suggest that this protein acts as a relative energy sink of the excitations in heterotrimers of Lhcb1/Lhcb2/Lhcb3. Minor differences in the amplitudes of some of the rate constants and in the absorption and fluorescence properties of some pigments were observed, which are ascribed to slight variations in the environment surrounding some of the chromophores depending on the isoform. The decay of the fluorescence was also similar for the three isoforms and multi-exponential, characterized by two major components in the ns regime and a minor one in the ps regime. In agreement with previous transient absorption measurements on native LHC II complexes, Chl b fi Chl a energy transfer exhibited very fast channels but at the same time a slow component (ps). The Chls absorbing at around 660 nm exhibited both fast energy transfer which we ascribe to transfer from 'red' Chl b towards 'red' Chl a and slow transfer from 'blue' Chl a towards 'red' Chl a. The results are discussed in the context of the new available atomic models for LHC II.

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Section: Absorption Ld Spectra and Time-resolved Fluorescencementioning

confidence: 55%

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

et al. 2006

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“…Absorption (Abs) spectra of Lhc proteins exhibit a markedly heterogeneous broadening in the range of 630-685 nm. From optical spectroscopic measurements, 8-11 spectral forms have been identified with reasonable certainty (8), while the number of bound Chls per monomer is in the range of 8-14 (6,9,10), suggesting that the spectral heterogeneity depends on the different protein environments in which individual chromophores are located.…”

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confidence: 85%

“…Due to the lack of information about the ring V and phytol chain esterification position ( Figure 5) in the tetrapyrrole rings determined in the LHCII structure (6), which would define the TMV, a free search in the space of possible chlorophyll orientations must discriminate among 8 8 cases for the CP29 protein. It is therefore important to reduce the number of acceptable solutions that will be evaluated.…”

Section: Cp29 Structuralmentioning

confidence: 99%

Orientation of Chlorophyll Transition Moments in the Higher-Plant Light-Harvesting Complex CP29

et al. 1999

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The Q y transition dipole moment vectors of all eight chlorophylls in the higher-plant antenna protein CP29 were calculated by an original method on the basis of linear dichroism and absorption spectroscopy. The contribution of individual chromophores was determined from difference spectra between wild type and mutant proteins in which a single chlorophyll has been removed by mutating pigmentbinding residues. Recombinant proteins were constructed by overexpressing the apoprotein in bacteria and refolding of the pigment-protein complex in vitro [Bassi, R., Croce, R., Cugini, D., and Sandonà, D. (1999) Proc. Natl. Acad. Sci. U.S.A. (in press)]. The spectroscopic data are interpreted on the basis of a protein structural model obtained via the homology with the major antenna complex LHCII [Kuhlbrandt, W., Wang, D. N., and Fujiyoshi, Y. (1994) Nature 367, 614-621]. The results allow us to determine the orientation of six chromophores within the protein structure. The orientations of the two remaining chromophores are inferred by considering the symmetry properties of CP29 and fitting steady state absorption and linear dichroism spectra by independent chlorophyll spectral forms. As a consequence, four "mixed" sites with different chlorophyll a and b binding affinities are identified in CP29. Geometrical data and the Förster mechanism for energy transfer suggest that excitation energy equilibrates rapidly among chlorophyll "pure" sites while energy preferentially flows outward from chlorophyll "mixed" sites. The orientation of the dipole moments of two chlorophyll molecules symmetrically located at the center of the protein and parallel to the carotenoid transition vectors suggests a role in energy transfer from xanthophyll to chlorophyll.In higher-plant chloroplasts, many pigment-binding proteins are inserted into the thylakoid membrane and organized into multisubunit complexes called photosystems. Photosystems (PS) 1 catalyze light absorption, the use of the excitation energy in transmembrane electron transport leading to the synthesis of ATP and NADPH. PS I and II are both composed of a chlorophyll a binding core complex and a chlorophyll a and b binding antenna. A detailed understanding of energy transfer processes in antenna and reaction centers requires knowledge of the distances between chromophores, of the mutual orientation between dipole transitions, and of the absorption and fluorescence energy levels and their distribution within the photosystems. In the case of PSII, considerable insight has been obtained from the topological organization of subunits (1-3) and from their spectral form decomposition (4, 5). Elucidation of the major antenna complex LHCII structure to 3.4 Å resolution (6) showed that many of the binding site environments are chemically distinct and that nearest-neighbor chlorophylls (Chl) are spaced 9-13 Å apart (center-center distance). The orientation of electronic transition dipole moments of the chromophores cannot yet be obtained from structural data, although linear dichrois...

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“…Whereas only two main absorption bands in the 640-700 nm region are observed at room temperature, as many as 6-9 bands were observed in absorption, circular dichroism, and linear dichroism spectra at 77 K (8), and today the spectral fingerprint consists of eleven features (11). Several earlier (sub)picosecond spectroscopic studies focusing on Chl b to Chl a energy transfer have been performed on LHCII trimers (15)(16)(17)(18)(19)(20).…”

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Energy Transfer in LHCII Monomers at 77K Studied by Sub-Picosecond Transient Absorption Spectroscopy

et al. 1997

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Energy transfer from chlorophyll b (Chl b) to chlorophyll a (Chl a) in monomeric preparations of light-harvesting complex II (LHCII) from spinach was studied at 77 K using pump-probe experiments. Sub-picosecond excitation pulses centered at 650 nm were used to excite preferentially Chl b and difference absorption spectra were detected from 630 to 700 nm. Two distinct Chl b to Chl a transfer times, ∼200 fs and 3 ps, were found. A clearly distinguishable energy transfer process between Chl a molecules occurred with a time constant of 18 ps. The LHCII monomer data are compared to previously obtained LHCII trimer data, and both data sets are fitted simultaneously using a global analysis fitting routine. Both sets could be described with the following time constants: 140 fs, 600 fs, 8 ps, 20 ps, and 2.9 ns. In both monomers and trimers 50% of the Chl b to Chl a transfer is ultrafast (<200 fs). However, for monomers this transfer occurs to Chl a molecules that absorb significantly more toward shorter wavelengths than for trimers. Part of the transfer from Chl b to Chl a that occurs with a time constant of 600 fs in trimers is slowed down to several picoseconds in monomers. However, it is argued that observed differences between monomers and trimers should be ascribed to the loss of some Chl a upon monomerization or a shift of the absorption maximum of one or several Chl a molecules. It is concluded that Chl b to Chl a transfer occurs only within monomeric subunits of the trimers and not between different subunits.Light-harvesting complex II (LHCII) 1 is the most abundant light-harvesting antenna pigment-protein complex of green plants. In nature it is believed to be organized in trimeric units and it binds 50% of the chlorophyll (CHl) present in the chloroplast (1). HPLC analysis has shown that each monomeric subunit binds 5-6 Chl b, 7-8 Chl a, and several xanthophyll (Xan) molecules: 2 luteins (Lut), 1 neoxanthin (Neo), and varying, substoichiometric amounts of violaxanthin (Vio) [see also Table 1, which is taken from (2)].The structure of the trimeric LHCII has been resolved to 3.4 Å using electron microscopy and electron diffraction of two-dimensional crystals (3). A significant part of the 26 kDa monomeric LHCII protein and the positions of 12 Chls and two luteins in the center of the protein were determined. However, the resolution was not high enough to distinguish between Chl a and Chl b, and the orientation of the lowestenergy electronic transition dipole moment (Q y ) of the individual chlorophylls cannot yet be assigned. Center to center distances between Chl a and Chl b within a monomer range from 8.3 to 10.5 Å. The role of the xanthophylls is, apart from light harvesting and structural stabilization of the complex, to quench Chl triplets to prevent the formation of singlet oxygen. This is only possible when the distance between the Chls and the Xans is small (4). On the basis of the idea that excitons are transferred very fast from Chl b to Chl a, so that Chl triplets are only formed on Chl a, a ...

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Spectroscopic properties of LHC-II, the main light-harvesting chlorophyll a/b protein complex from chloroplast membranes

Cited by 169 publications

References 46 publications

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

A comparison of the three isoforms of the light-harvesting complex II using transient absorption and time-resolved fluorescence measurements

Orientation of Chlorophyll Transition Moments in the Higher-Plant Light-Harvesting Complex CP29

Energy Transfer in LHCII Monomers at 77K Studied by Sub-Picosecond Transient Absorption Spectroscopy

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