scholarly journals Structure of the far-red light utilizing photosystem I of Acaryochloris

2020 ◽  
Author(s):  
Tasuku Hamaguchi ◽  
Keisuke Kawakami ◽  
Kyoko Shinzawa-Itoh ◽  
Natsuko Inoue-Kashino ◽  
Shigeru Itoh ◽  
...  
Keyword(s):  
Photosystem I ◽  
Red Light ◽  
Primary Electron ◽  
Oxygenic Photosynthesis ◽  
Energy Yield ◽  
Type I ◽  
Cryo Electron Microscopy ◽  
Primary Electron Acceptor ◽  
Acaryochloris Marina ◽  
Electron Carriers

Abstract Acaryochloris marina is a cyanobacterium that can, uniquely, use far-red light for oxygenic photosynthesis. Here, we report the structure of the photosystem I reaction center of A. marina determined by cryo-electron microscopy at 2.5 Å resolution. The structure reveals a unique arrangement of electron carriers and light harvesting pigments. The primary electron donor P740 is a dimer of chlorophyll d/d′ and the primary electron acceptor pheophytin a, a metal-less chlorin different from the chlorophyll a common to all other oxygenic type I reaction centers. The architecture of the 11 subunits and identity of key components help explain how the low energy yield from far-red light is efficiently utilized for driving oxygenic photosynthesis.

scholarly journals Structure of the far-red light utilizing photosystem I of Acaryochloris marina

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tasuku Hamaguchi ◽  
Keisuke Kawakami ◽  
Kyoko Shinzawa-Itoh ◽  
Natsuko Inoue-Kashino ◽  
Shigeru Itoh ◽  
...  
Keyword(s):  
Reaction Center ◽  
Photosystem I ◽  
Red Light ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Oxygenic Photosynthesis ◽  
Energy Yield ◽  
Type I ◽  
Cyanobacterial Species ◽  
Acaryochloris Marina

AbstractAcaryochloris marina is one of the cyanobacterial species that can use far-red light to drive photochemical reactions for oxygenic photosynthesis. Here, we report the structure of A. marina photosystem I (PSI) reaction center, determined by cryo-electron microscopy at 2.58 Å resolution. The structure reveals an arrangement of electron carriers and light-harvesting pigments distinct from other type I reaction centers. The paired chlorophyll, or special pair (also referred to as P740 in this case), is a dimer of chlorophyll d and its epimer chlorophyll d′. The primary electron acceptor is pheophytin a, a metal-less chlorin. We show the architecture of this PSI reaction center is composed of 11 subunits and we identify key components that help explain how the low energy yield from far-red light is efficiently utilized for driving oxygenic photosynthesis.

scholarly journals Structure of the far-red light utilizing photosystem I of Acaryochloris marina

2021 ◽  
Author(s):  
Tasuku Hamaguchi ◽  
Keisuke Kawakami ◽  
Kyoko Shinzawa-Itoh ◽  
Natsuko Inoue-Kashino ◽  
Shigeru Itoh ◽  
...  
Keyword(s):  
Reaction Center ◽  
Photosystem I ◽  
Red Light ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Reaction Centers ◽  
Oxygenic Photosynthesis ◽  
Energy Yield ◽  
Type I ◽  
Acaryochloris Marina

Abstract Acaryochloris marina is one of the cyanobacteria that can use far-red light to drive photochemical reactions for oxygenic photosynthesis. Here, we report the structure of the photosystem I reaction center of A. marina determined by cryo-electron microscopy at 2.5 Å resolution. The structure reveals an arrangement of electron carriers and light-harvesting pigments different from other type I reaction centers. The paired chlorophyll, so-called special pair, of P740 is a dimer of chlorophyll d/d′ and the primary electron acceptor is pheophytin a, a metal-less chlorin different from the chlorophyll a common to all other type I reaction centers. Here we show the architecture of the photosystem I reaction center is composed of 11 subunits and identify key components that help explain how the low energy yield from far-red light is efficiently utilized for driving oxygenic photosynthesis.

scholarly journals The structure of Photosystem I acclimated to far-red light illuminates an ecologically important acclimation process in photosynthesis

2020 ◽  
Vol 6 (6) ◽  
pp. eaay6415 ◽  
Author(s):  
Christopher Gisriel ◽  
Gaozhong Shen ◽  
Vasily Kurashov ◽  
Ming-Yang Ho ◽  
Shangji Zhang ◽  
...  
Keyword(s):  
Photosystem I ◽  
Binding Sites ◽  
Structural Changes ◽  
Red Light ◽  
Oxygenic Photosynthesis ◽  
Cryo Electron Microscopy ◽  
Photosynthetic Proteins ◽  
Functional Differences ◽  
Light Utilization ◽  
Chlorophyll F

Phototrophic organisms are superbly adapted to different light environments but often must acclimate to challenging competition for visible light wavelengths in their niches. Some cyanobacteria overcome this challenge by expressing paralogous photosynthetic proteins and by synthesizing and incorporating ~8% chlorophyll f into their Photosystem I (PSI) complexes, enabling them to grow under far-red light (FRL). We solved the structure of FRL-acclimated PSI from the cyanobacterium Fischerella thermalis PCC 7521 by single-particle, cryo–electron microscopy to understand its structural and functional differences. Four binding sites occupied by chlorophyll f are proposed. Subtle structural changes enable FRL-adapted PSI to extend light utilization for oxygenic photosynthesis to nearly 800 nm. This structure provides a platform for understanding FRL-driven photosynthesis and illustrates the robustness of adaptive and acclimation mechanisms in nature.

scholarly journals Early Archean origin of heterodimeric Photosystem I

2017 ◽  
Author(s):  
Tanai Cardona
Keyword(s):  
Gene Duplication ◽  
Photosystem I ◽  
Water Oxidation ◽  
Duplication Event ◽  
Oxygenic Photosynthesis ◽  
Recent Common Ancestor ◽  
Type I ◽  
Reaction Centre ◽  
Gene Duplication Event ◽  
Most Recent Common Ancestor

AbstractWhen and how oxygenic photosynthesis originated remains controversial. Wide uncertainties exist for the earliest detection of biogenic oxygen in the geochemical record or the origin of water oxidation in ancestral lineages of the phylum Cyanobacteria. A unique trait of oxygenic photosynthesis is that the process uses a Type I reaction centre with a heterodimeric core, also known as Photosystem I, made of two distinct but homologous subunits, PsaA and PsaB. In contrast, all other known Type I reaction centres in anoxygenic phototrophs have a homodimeric core. A compelling hypothesis for the evolution of a heterodimeric Type I reaction centre is that the gene duplication that allowed the divergence of PsaA and PsaB was an adaptation to incorporate photoprotective mechanisms against the formation of reactive oxygen species, therefore occurring after the origin of water oxidation to oxygen. Here I show, using sequence comparisons and Bayesian relaxed molecular clocks that this gene duplication event may have occurred in the early Archean more than 3.4 billion years ago, long before the most recent common ancestor of crown group Cyanobacteria and the Great Oxidation Event. If the origin of water oxidation predated this gene duplication event, then that would place primordial forms of oxygenic photosynthesis at a very early stage in the evolutionary history of life.

The site of electron transport inhibition by bentazon (3-isopropyl-1H-2,1,3-benzothiadiazin-(4)3H-one 2,2-dioxide) in isolated chloroplasts

1982 ◽  
Vol 60 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Rungsit Suwanketnikom ◽  
Kriton K. Hatzios ◽  
Donald Penner ◽  
Duncan Bell
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Photosystem I ◽  
Electron Acceptor ◽  
Photosynthetic Electron Transport ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Spinacea Oleracea ◽  
Primary Electron Acceptor ◽  
Isolated Chloroplasts

The effect of bentazon (3-isopropyl-1H-2,1,3-benzathiadiazin-(4)3H-one 2,2-dioxide) on various photochemical reactions of isolated spinach (Spinacea oleracea L.) chloroplasts was studied at concentrations 0, 5, 15, 45, and 135 μM. Bentazon at a concentration of 135 μM strongly inhibited uncoupled electron transport from water to ferricyanide or to methylviologen with inhibition percentages greater than 90%. Photosystem II mediated electron transport from water to oxidized diaminodurene, with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB) blocking photosystem I, was also strongly inhibited by bentazon at 135 μM but less with lower concentrations of bentazon. Photosystem I mediated transfer of electrons from diaminodurene to methylviologen, with 3,4-dichlorophenyl-1,1-dimethylurea (DCMU) blocking photosystem II, was not inhibited by bentazon at any concentration examined. Transfer of electrons from catechol to methylviologen in hydroxylamine-treated chloroplasts was inhibited by bentazon, and the inhibition percentages were again concentration dependent. The data indicate that the site of bentazon inhibition of the photosynthetic electron transport is at the reducing side of photosystem II, between the primary electron acceptor Q and plastoquinone.

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