Light harvesting in oxygenic photosynthesis: Structural biology meets spectroscopy

Croce, Roberta; Amerongen, Herbert van

doi:10.1126/science.aay2058

Cited by 242 publications

(238 citation statements)

References 110 publications

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“…During the first steps of the photosynthetic process, solar photons are absorbed by specialized light-harvesting complexes (LHCs), and the resulting excitation energy is transferred to reaction center pigments, where it is converted into a chemical potential. In low-light conditions, most of the photons absorbed lead to a charge separation event at the reaction center ( 1 , 2 ). However, when the absorbed energy is in excess of that which can be used for energy transduction, the overaccumulation of excited states can result in damage to the photosynthetic membrane, in particular, via the production of reactive oxygen species.…”

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confidence: 99%

A new, unquenched intermediate of LHCII

Cheng

Streckaitė

et al. 2021

Journal of Biological Chemistry

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When plants are exposed to high-light conditions, the potentially harmful excess energy is dissipated as heat, a process called non-photochemical quenching. Efficient energy dissipation can also be induced in the major light-harvesting complex of photosystem II (LHCII) in vitro , by altering the structure and interactions of several bound cofactors. In both cases, the extent of quenching has been correlated with conformational changes (twisting) affecting two bound carotenoids, neoxanthin, and one of the two luteins (in site L1). This lutein is directly involved in the quenching process, whereas neoxanthin senses the overall change in state without playing a direct role in energy dissipation. Here we describe the isolation of an intermediate state of LHCII, using the detergent n -dodecyl-α-D-maltoside, which exhibits the twisting of neoxanthin (along with changes in chlorophyll–protein interactions), in the absence of the L1 change or corresponding quenching. We demonstrate that neoxanthin is actually a reporter of the LHCII environment—probably reflecting a large-scale conformational change in the protein—whereas the appearance of excitation energy quenching is concomitant with the configuration change of the L1 carotenoid only, reflecting changes on a smaller scale. This unquenched LHCII intermediate, described here for the first time, provides for a deeper understanding of the molecular mechanism of quenching.

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confidence: 99%

A new, unquenched intermediate of LHCII

Cheng

Streckaitė

et al. 2021

Journal of Biological Chemistry

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“…In photosynthesis, the major light-harvesting complex II (LHCII) serves as the principal solar energy collector transferring the sunlight energy toward the reaction center of the photosystems. 1 LHCII is located in the thylakoid membrane of the chloroplast, normally presenting a trimer structure with each monomer unit binding a total of 18 pigments: six chlorophylls b (Chlb), eight chlorophylls a (Chla), and four carotenoid (Car) molecules. 2 These chromophores are responsible for sunlight absorption and are grouped into Chl–Chl and/or Chl–Car clusters according to the intensity of their excitonic interactions, given their relative orientation and proximity in space.…”

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confidence: 99%

Understanding the Relation between Structural and Spectral Properties of Light-Harvesting Complex II

et al. 2021

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Light-harvesting complex II (LHCII) is a pigment–protein complex present in higher plants and green algae. LHCII represents the main site of light absorption, and its role is to transfer the excitation energy toward the photosynthetic reaction centers, where primary energy conversion reactions take place. The optical properties of LHCII are known to depend on protein conformation. However, the relation between the structural and spectroscopic properties of the pigments is not fully understood yet. In this respect, previous classical molecular dynamics simulations of LHCII in a model membrane [ Sci. Rep. 2015 , 5 , 1–10] have shown that the configuration and excitonic coupling of a chlorophyll (Chl) dimer functioning as the main terminal emitter of the complex are particularly sensitive to conformational changes. Here, we use quantum chemistry calculations to investigate in greater detail the effect of pigment–pigment interactions on the excited-state landscape. While most previous studies have used a local picture in which electrons are localized on single pigments, here we achieve a more accurate description of the Chl dimer by adopting a supramolecular picture where time-dependent density functional theory is applied to the whole system at once. Our results show that specific dimer configurations characterized by shorter inter-pigment distances can result in a sizable intensity decrease (up to 36%) of the Chl absorption bands in the visible spectral region. Such a decrease can be predicted only when accounting for Chl–Chl charge-transfer excitations, which is possible using the above-mentioned supramolecular approach. The charge-transfer character of the excitations is quantified by two types of analyses: one focusing on the composition of the excitations and the other directly on the observable total absorption intensities.

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“…Light is an important and ubiquitous signal in terrestrial and aquatic ecosystems, and the ability to sense, respond and adapt to light is crucial for most living organisms, including bacteria. Photosynthetic bacteria capture and convert light, an essential energy source, to chemical energy for cellular utilization, but light is also important for several other cellular processes in both phototrophic and non-phototrophic bacteria [ 1 , 2 , 3 , 4 , 5 ]. Thus, light is linked to many bacterial responses such as phototaxis, development, virulence, circadian rhythms and UV-induced DNA damage repair [ 4 , 5 , 6 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

Light-Triggered Carotenogenesis in Myxococcus xanthus: New Paradigms in Photosensory Signaling, Transduction and Gene Regulation

et al. 2021

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Myxobacteria are Gram-negative δ-proteobacteria found predominantly in terrestrial habitats and often brightly colored due to the biosynthesis of carotenoids. Carotenoids are lipophilic isoprenoid pigments that protect cells from damage and death by quenching highly reactive and toxic oxidative species, like singlet oxygen, generated upon growth under light. The model myxobacterium Myxococcus xanthus turns from yellow in the dark to red upon exposure to light because of the photoinduction of carotenoid biosynthesis. How light is sensed and transduced to bring about regulated carotenogenesis in order to combat photooxidative stress has been extensively investigated in M. xanthus using genetic, biochemical and high-resolution structural methods. These studies have unearthed new paradigms in bacterial light sensing, signal transduction and gene regulation, and have led to the discovery of prototypical members of widely distributed protein families with novel functions. Major advances have been made over the last decade in elucidating the molecular mechanisms underlying the light-dependent signaling and regulation of the transcriptional response leading to carotenogenesis in M. xanthus. This review aims to provide an up-to-date overview of these findings and their significance.

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Light harvesting in oxygenic photosynthesis: Structural biology meets spectroscopy

Cited by 242 publications

References 110 publications

A new, unquenched intermediate of LHCII

A new, unquenched intermediate of LHCII

Understanding the Relation between Structural and Spectral Properties of Light-Harvesting Complex II

Light-Triggered Carotenogenesis in Myxococcus xanthus: New Paradigms in Photosensory Signaling, Transduction and Gene Regulation

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