The structure of a plant photosystem I supercomplex at 3.4 Å resolution

Amunts, Alexey; Drory, Omri; Nelson, Nathan

doi:10.1038/nature05687

Cited by 457 publications

(381 citation statements)

References 52 publications

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“…However, we consider this to be unlikely for several reasons: First, the crystal structure of PSI (Amunts et al, 2007) shows that the lumenal protrusions of this complex are <1 nm, whereas the interaction hot spots we detect consistently label features 3 nm in height, a difference easily resolved by the 0.1 nm z-resolution of the AFM; second, in the event of binding to PSI, we would predict that the prereduced Pc-functionalized AFM probes would detect a similar number of interactions when in fact they were greatly decreased compared with the preoxidized probes. The fact we observed very few interactions of prereduced Pc-functionalized probes with the PSI complexes in DG and SG membranes suggests we could not maintain a photo-oxidized state, likely because we did not include a PSI electron acceptor.…”

Section: Affinity-mapping Afm Using Pc-functionalized Afm Probes Allomentioning

confidence: 99%

Nanodomains of Cytochromeb 6 fand Photosystem II Complexes in Spinach Grana Thylakoid Membranes

et al. 2014

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The cytochrome b 6 f (cytb 6 f) complex plays a central role in photosynthesis, coupling electron transport between photosystem II (PSII) and photosystem I to the generation of a transmembrane proton gradient used for the biosynthesis of ATP. Photosynthesis relies on rapid shuttling of electrons by plastoquinone (PQ) molecules between PSII and cytb 6 f complexes in the lipid phase of the thylakoid membrane. Thus, the relative membrane location of these complexes is crucial, yet remains unknown. Here, we exploit the selective binding of the electron transfer protein plastocyanin (Pc) to the lumenal membrane surface of the cytb 6 f complex using a Pc-functionalized atomic force microscope (AFM) probe to identify the position of cytb 6 f complexes in grana thylakoid membranes from spinach (Spinacia oleracea). This affinity-mapping AFM method directly correlates membrane surface topography with Pc-cytb 6 f interactions, allowing us to construct a map of the grana thylakoid membrane that reveals nanodomains of colocalized PSII and cytb6f complexes. We suggest that the close proximity between PSII and cytb 6 f complexes integrates solar energy conversion and electron transfer by fostering short-range diffusion of PQ in the protein-crowded thylakoid membrane, thereby optimizing photosynthetic efficiency.

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Section: Affinity-mapping Afm Using Pc-functionalized Afm Probes Allomentioning

confidence: 99%

Nanodomains of Cytochromeb 6 fand Photosystem II Complexes in Spinach Grana Thylakoid Membranes

et al. 2014

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“…The major outer antenna of PSII, often referred to as LHCII, is a trimer of any combination of the three very similar complexes Lhcb1-3, whereas the minor antenna consists of the three monomers Lhcb4-6, also known as CP29, CP26, and CP24, respectively. The proteins of all these complexes show a high structural homology (18)(19)(20)(21) and coordinate the same pigments-namely, chlorophyll (Chl) a and b molecules and a few carotenoids-in a comparable organization. Despite their structural and compositional similarities, Lhcas exhibit considerably red-shifted and broadened fluorescence emission with respect to Lhcbs.…”

mentioning

confidence: 99%

Conformational switching explains the intrinsic multifunctionality of plant light-harvesting complexes

Krüger

Wientjes

Croce

et al. 2011

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

104

125

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The light-harvesting complexes of photosystem I and II (Lhcas and Lhcbs) of plants display a high structural homology and similar pigment content and organization. Yet, the spectroscopic properties of these complexes, and accordingly their functionality, differ substantially. This difference is primarily due to the charge-transfer (CT) character of a chlorophyll dimer in all Lhcas, which mixes with the excitonic states of these complexes, whereas this CT character is generally absent in Lhcbs. By means of single-molecule spectroscopy near room temperature, we demonstrate that the presence or absence of such a CT state in Lhcas and Lhcbs can occasionally be reversed; i.e., these complexes are able to interconvert conformationally to quasi-stable spectral states that resemble the Lhcs of the other photosystem. The high structural similarity of all the Lhca and Lhcb proteins suggests that the stable conformational states that give rise to the mixed CT-excitonic state are similar for all these proteins, and similarly for the conformations that involve no CT state. This indicates that the specific functions related to Lhca and Lhcb complexes are realized by different stable conformations of a single generic protein structure. We propose that this functionality is modulated and controlled by the protein environment.protein multifunctionality | red forms A lthough conformational changes are essential for the function of proteins, little is known about their complex structural dynamics. Protein motions can partially be described by dynamic disorder in the crystalline, glass-like, or liquid states of matter (1-3). A feasible conceptual framework has been developed to visualize these dynamics as transitions between hierarchically ordered minima in the high-dimensional energy landscape of the protein (4, 5). Such a landscape represents all possible energy states as a function of the protein's conformation. The local minima, which signify conformational substates (CSs), are divided by energy barriers into different tiers. The order of a tier is characterized by an average barrier height, a higher barrier of which corresponds to a lower rate of conformational transitions (6). Protein-embedded pigments often serve as effective probes of conformational changes. In particular, strong intrapigment interactions in pigment aggregates can considerably increase the sensitivity of the pigments to the local environment (7). As a result, transitions between CSs are reflected as changes in the pigment electronic states and can be observed as distinct shifts in their absorption and emission energies. In conventional spectroscopy on large ensembles of proteins, energy equilibration after an excitation perturbation is monitored as the average of a very large number of possible trajectories on the energy landscapes of many similar proteins. In contrast, in single-molecule spectroscopy (SMS), the energy landscape of a single protein can be probed. For various pigment-protein complexes, this technique has proven successful to identify conform...

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“…This gives rise to an asymmetric conformation of the complex, as all 4 LHCI subunits are located in one side of the complex. The opposite side is occupied by PsaL and PsaH, of which, PsaH has been suggested to serve as a docking site for mobile LHCII possibly migrated from PSII upon state-transitions (Takahashi et al, 2006;Amunts et al, 2007). This subunit is not present in cyanobacterial as well as red algal PSI, since the antennae of PSII in both organisms are membrane-peripheral phycobilisomes instead of LHCII.…”

Section: Photosystem Imentioning

confidence: 99%

“…In Figure 5A, the protein composition of PSI from C. caldarium is compared with that of the cyanobacterial PSI from T. vulcanus. The crystal structure of PSI from both cyanobacteria and higher plants has been reported (Jordan et al, 2001;Amunts et al, 2007). Figure 5B shows the crystal structure of PSI from pea at a 3.4 Å resolution (Amunts et al, 2007).…”

Section: Photosystem Imentioning

confidence: 99%

“…The crystal structure of PSI from both cyanobacteria and higher plants has been reported (Jordan et al, 2001;Amunts et al, 2007). Figure 5B shows the crystal structure of PSI from pea at a 3.4 Å resolution (Amunts et al, 2007). The core part of pea PSI contains 13 subunits, namely, PsaA, B, C, D, E, F, G, H, I, J, K, L, and N. In addition, 4 LHCI subunits designated LHC1-4, are associated in the periphery of the complex.…”

Section: Photosystem Imentioning

confidence: 99%

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Mechanisms of Acido-Tolerance and Characteristics of Photosystems in an Acidophilic and Thermophilic Red Alga, Cyanidium Caldarium

Enami

Adachi

Shen

2010

Cellular Origin, Life in Extreme Habitats and Astrobiology

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In this chapter, we describe the mechanisms of acido-tolerance in an acido-and thermo-philic red alga, Cyanidium caldarium. In spite of the extremely acidic environments it inhabits, the intracellular pH of Cyanidium cells is kept neutral by pumping out the protons previously leaked into the cells according to the steep pH gradient. The H + pump is driven by the plasma membrane ATPase, utilizing intracellular ATP produced by both oxidative phosphorylation and cyclic photophosphorylation via photosystem I. We also describe the characteristics and function of the two photosystems, Photosystem I (PSI) and II (PSII) in Cyanidium caldarium in comparison with those of cyanobacteria, other eukaryotic algae and higher plants, based on the crystal structures of the two complexes reported so far.

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The structure of a plant photosystem I supercomplex at 3.4 Å resolution

Cited by 457 publications

References 52 publications

Nanodomains of Cytochromeb 6 fand Photosystem II Complexes in Spinach Grana Thylakoid Membranes

Nanodomains of Cytochromeb 6 fand Photosystem II Complexes in Spinach Grana Thylakoid Membranes

Conformational switching explains the intrinsic multifunctionality of plant light-harvesting complexes

Mechanisms of Acido-Tolerance and Characteristics of Photosystems in an Acidophilic and Thermophilic Red Alga, Cyanidium Caldarium

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