A previously unrecognized membrane protein in the Rhodobacter sphaeroides LH1-RC photocomplex

Tani, Kazuhide; Nagashima, Kenji V. P.; Kanno, Ryo; Kawamura, Saki; Kikuchi, Riku; Hall, Malgorzata; Yu, Long-Jiang; Kimura, Yukihiro; Madigan, Michael T.; Mizoguchi, Akira; Humbel, Bruno M.; Wang-Otomo, Zheng-Yu

doi:10.1038/s41467-021-26561-9

Cited by 30 publications

(46 citation statements)

References 67 publications

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“…6). The resolved core RCs have a very conserved structure, highly similar to other described RCs from purple bacteria 7,23,38,39 . Also, protein Y is resolved in the Rca.…”

Section: Rc-lh1-pufx Dimersupporting

confidence: 52%

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Cryo-EM structure of the Rhodobaca bogoriensis RC-LH1-PufX dimeric complex at 2.9 Å

Semchonok

Siponen

Tüting

et al. 2022

Preprint

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The reaction centre-light harvesting 1 (RC-LH1) complex is essential for converting light into proton motive force in photosynthetic bacteria. RC-LH1 is a monomer in most purple bacteria, but in Rhodobacter species, it is a dimer. Its assembly depends on an accessory polypeptide (PufX) and, ultimately, on photosynthetic growth. To date, knowledge on the RC-LH1-PufX structure, where the dimer has two incomplete 'C'-shaped antenna rings surrounding an RC, is mainly limited to the model organism Rhodobacter sphaeroides. Here we present a cryo-electron microscopy structure at 2.9 angstrom from Rhodobaca bogorensis strain LBB1. RCs are surrounded by 30 antennas and incorporate protein Y and PufX. RCs are stably connected by PufX, which self-interacts, electrostatically attracts cytochrome c2 (cyt c2) and forms extensive networks with co-factors. This structure underlines coordinated energy transfer in a combinatorial manner, providing a basis to describe bacterial photosynthesis within a dimeric photosynthetic apparatus.

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“…6). The resolved core RCs have a very conserved structure, highly similar to other described RCs from purple bacteria 7,23,38,39 . Also, protein Y is resolved in the Rca.…”

Section: Rc-lh1-pufx Dimersupporting

confidence: 52%

“…Overall, the resolved RC is composed of the L, H, and M protein subunits, protein U 38 (also named protein Y 23 whose sequence is different from that of R. sphaeroides ) 4 BChl a, 3 Bacteriopheophytin a (BPhe a), 5 quinones (Q-10), 1 Spno, 4 PE lipids (3-sn-PE) and a Fe atom (Fig. 6a, Extended Data Fig.…”

Section: Resultsmentioning

confidence: 99%

Cryo-EM structure of the Rhodobaca bogoriensis RC-LH1-PufX dimeric complex at 2.9 Å

Semchonok

Siponen

Tüting

et al. 2022

Preprint

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“…This position is close to the location of the previously assigned PufX polypeptide in the low-resolution crystal and cryo-EM structures 18 , 20 . We identified this protein as RSP_7571 (termed PufY, equivalent to the Protein-U 42 or Protein-Y 43 reported recently), based on the perfect match of its sequence with the cryo-EM density map (Fig. 3b , Fig.…”

Section: Resultsmentioning

confidence: 99%

Structural basis for the assembly and quinone transport mechanisms of the dimeric photosynthetic RC–LH1 supercomplex

et al. 2022

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The reaction center (RC) and light-harvesting complex 1 (LH1) form a RC–LH1 core supercomplex that is vital for the primary reactions of photosynthesis in purple phototrophic bacteria. Some species possess the dimeric RC–LH1 complex with a transmembrane polypeptide PufX, representing the largest photosynthetic complex in anoxygenic phototrophs. However, the details of the architecture and assembly mechanism of the RC–LH1 dimer are unclear. Here we report seven cryo-electron microscopy (cryo-EM) structures of RC–LH1 supercomplexes from Rhodobacter sphaeroides. Our structures reveal that two PufX polypeptides are positioned in the center of the S-shaped RC–LH1 dimer, interlocking association between the components and mediating RC–LH1 dimerization. Moreover, we identify another transmembrane peptide, designated PufY, which is located between the RC and LH1 subunits near the LH1 opening. PufY binds a quinone molecule and prevents LH1 subunits from completely encircling the RC, creating a channel for quinone/quinol exchange. Genetic mutagenesis, cryo-EM structures, and computational simulations provide a mechanistic understanding of the assembly and electron transport pathways of the RC–LH1 dimer and elucidate the roles of individual components in ensuring the structural and functional integrity of the photosynthetic supercomplex.

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“…Some LH1 antennas also contain additional subunits; the Rhodopseudomonas palustris LH1 ring contains a single transmembrane helix known as protein W [11,12], LH1 from Rhodobacter spp. contains a PufX polypeptide [13][14][15], and a further subgroup of these organisms additionally contain PufY [16][17][18]. These polypeptides create a channel in the LH1 ring allowing quinone/quinol exchange between the RC and the cytochrome bc1 complex [19,20].…”

Section: Introductionmentioning

confidence: 99%

The role of the γ subunit in the photosystem of the lowest-energy phototrophs

Namoon

Rudling

Canniffe

2022

Preprint

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Purple phototrophic bacteria use a core "photosystem" consisting of light harvesting antenna complex 1 (LH1) surrounding the reaction centre (RC), which primarily absorbs far-red/near-infrared light and converts it to chemical energy. Species in the Blastochloris genus, which are able to use light >1000nm for photosynthesis, use bacteriochlorophyll (BChl) b rather than the more common BChl a as their major photopigment, and also uniquely assemble LH1 with an additional polypeptide subunit, LH1γ, encoded by multiple open reading frames in their genomes. In order to assign a role to this subunit, we deleted the four LH1γ-encoding genes in the model Blastochloris viridis. Interestingly, growth under halogen bulbs routinely used for cultivation of anoxygenic phototrophs yielded cells displaying an absorption maximum of 825 nm, similar to that of the RC complex without LH1, but growth under white light from fluorescent bulbs yielded cells with an absorption maximum at 972 nm. HPLC analysis of pigment composition and sucrose density gradient fractionation demonstrate that the mutant grown in white light assembles RC-LH1, albeit with an absorption maximum blue-shifted by 46 nm relative to the WT complex. Wavelengths between 900-1000 nm transmit poorly through the atmosphere due to strong absorption by water, thus our results provide an evolutionary rationale for the incorporation of the γ subunit into the LH1 ring; this polypeptide red-shifts the absorption maximum of the complex to a range of the spectrum where the photons are of lower energy but are more abundant. Finally, we transformed the mutant with plasmids carrying genes encoding natural LH1γ variants and demonstrate that the polypeptide found in the WT complex red-shifts absorption back to 1018 nm, but incorporation of a distantly-related variant results in only a moderate red-shift. This result suggests that tuning the absorption maximum of this organism is possible, and may permit light capture past the current low-energy limit of natural photosynthesis.

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A previously unrecognized membrane protein in the Rhodobacter sphaeroides LH1-RC photocomplex

Cited by 30 publications

References 67 publications

Cryo-EM structure of the Rhodobaca bogoriensis RC-LH1-PufX dimeric complex at 2.9 Å

Cryo-EM structure of the Rhodobaca bogoriensis RC-LH1-PufX dimeric complex at 2.9 Å

Structural basis for the assembly and quinone transport mechanisms of the dimeric photosynthetic RC–LH1 supercomplex

The role of the γ subunit in the photosystem of the lowest-energy phototrophs

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