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Cryo-EM structure of the dimeric Rhodobacter sphaeroides RC-LH1 core complex at 2.9 Å: the structural basis for dimerisation
- Source :
- Biochemical Journal
-
Abstract
- The dimeric reaction centre light-harvesting 1 (RC-LH1) core complex of Rhodobacter sphaeroides converts absorbed light energy to a charge separation, and then it reduces a quinone electron and proton acceptor to a quinol. The angle between the two monomers imposes a bent configuration on the dimer complex, which exerts a major influence on the curvature of the membrane vesicles, known as chromatophores, where the light-driven photosynthetic reactions take place. To investigate the dimerisation interface between two RC-LH1 monomers, we determined the cryogenic electron microscopy structure of the dimeric complex at 2.9 Å resolution. The structure shows that each monomer consists of a central RC partly enclosed by a 14-subunit LH1 ring held in an open state by PufX and protein-Y polypeptides, thus enabling quinones to enter and leave the complex. Two monomers are brought together through N-terminal interactions between PufX polypeptides on the cytoplasmic side of the complex, augmented by two novel transmembrane polypeptides, designated protein-Z, that bind to the outer faces of the two central LH1 β polypeptides. The precise fit at the dimer interface, enabled by PufX and protein-Z, by C-terminal interactions between opposing LH1 αβ subunits, and by a series of interactions with a bound sulfoquinovosyl diacylglycerol lipid, bring together each monomer creating an S-shaped array of 28 bacteriochlorophylls. The seamless join between the two sets of LH1 bacteriochlorophylls provides a path for excitation energy absorbed by one half of the complex to migrate across the dimer interface to the other half.
- Subjects :
- Cryo-electron microscopy
Dimer
Biophysics
Light-Harvesting Protein Complexes
Rhodobacter sphaeroides
Bioenergetics
Ring (chemistry)
Biochemistry
Sulfoquinovosyl diacylglycerol
chemistry.chemical_compound
Bacterial Proteins
Structural Biology
light harvesting
transmembrane proteins
Photosynthesis
Molecular Biology
Research Articles
biology
Molecular Structure
carotenoids
Cell Biology
biology.organism_classification
Quinone
reaction centre
Crystallography
Monomer
chemistry
Bacteriochlorophyll
bacteriochlorophylls
Dimerization
Subjects
Details
- Language :
- English
- ISSN :
- 14708728 and 02646021
- Volume :
- 478
- Issue :
- 21
- Database :
- OpenAIRE
- Journal :
- Biochemical Journal
- Accession number :
- edsair.doi.dedup.....98d1739b57fae6ad18290a1d3a8f8edb
- Full Text :
- https://doi.org/10.1042/bcj20210696