Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.10.21.349431v1?rss=1 Authors: Gardiner, A. T., Naydenova, K., Hartmann, P. C., Nguyen-Phan, T. C., Russo, C. J., Sader, K., Hunter, C. N., Cogdell, R. J., Qian, P. Abstract: We report the 2.4 Angstrom resolution structure of the light harvesting 2 complex (LH2) from Marichromatium (Mch.) purpuratum determined by electron cryo-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. Two sets of distinct carotenoids are identified in the structure, and a network of energy transfer pathways from the carotenoids to bacteriochlorophyll a molecules is shown. 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. Copy rights belong to original authors. Visit the link for more info