EMD-32062
Rba sphaeroides PufX-KO RC-LH1
EMD-32062
Single-particle4.2 Å
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Map released: 04/05/2022
Last modified: 19/06/2024
Sample Organism:
Cereibacter sphaeroides 2.4.1
Sample: Rhodobacter sphaeroides PufX-KO RC-LH1
Fitted models: 7voy (Avg. Q-score: 0.372)
Deposition Authors: Bracun L
,
Yamagata A
Sample: Rhodobacter sphaeroides PufX-KO RC-LH1
Fitted models: 7voy (Avg. Q-score: 0.372)
Deposition Authors: Bracun L
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Structural basis for the assembly and quinone transport mechanisms of the dimeric photosynthetic RC-LH1 supercomplex.
Cao P,
Bracun L
,
Yamagata A
,
Christianson BM,
Negami T,
Zou B,
Terada T
,
Canniffe DP
,
Shirouzu M
,
Li M
,
Liu LN
(2022) Nat Commun , 13 , 1977 - 1977
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(2022) Nat Commun , 13 , 1977 - 1977
Abstract:
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.
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.