The 2.4 Å cryo-EM structure of a heptameric light-harvesting 2 complex reveals two carotenoid energy transfer pathways.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33579696.
- Also identified by DOI 10.1126/sciadv.abe4650 and PMC identifier 7880592.
- Licence recorded as CC BY.
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Abstract
We report the 2.4 Ångström resolution structure of the light-harvesting 2 (LH2) complex from <i>Marichromatium</i> (<i>Mch.</i>) <i>purpuratum</i> determined by cryogenic electron microscopy. The structure contains a heptameric ring that is unique among all known LH2 structures, explaining the unusual spectroscopic properties of this bacterial antenna complex. We identify two sets of distinct carotenoids in the structure and describe a network of energy transfer pathways from the carotenoids to bacteriochlorophyll <i>a</i> molecules. The geometry imposed by the heptameric ring controls the resonant coupling of the long-wavelength energy absorption band. Together, these details reveal key aspects of the assembly and oligomeric form of purple bacterial LH2 complexes that were previously inaccessible by any technique.