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November, 2021

Many bacteria that use light as part of their metabolism use light-harvesting 2 (LH2) antenna complexes to augment the collection of solar energy. Despite its frequent role as a model for such complexes, there has been no 3D structure available for the LH2 from the purple phototroph Rhodobacter sphaeroides. We used cryo-electron microscopy to determine the structure of this LH2 antenna at 2.1 Å resolution. We identify nine sub-units, each one binding to three chlorophyll molecules and one carotenoid. The high resolution model of this structure reveals all of the interpigment and pigment–protein interactions that promote the assembly and energy-transfer properties of this complex.

This work was carried out in collaboration between the University of Sheffield, the cryo-EM specialists from ThermoFisher involved in the running of the Krios installed in MSM and the EM suite.


(Left) Model of the light harvesting compound, with central channel and subunits visible from the compound’s axis

(Right) Electron density map from cryo-EM

P. Qian, D.J.K. Swainsbury, T.I. Croll, P. Castro-Hartmann, G. Divitini, K. Sader, and C.N. Hunter, "Cryo-EM Structure of the Rhodobacter sphaeroides Light-Harvesting 2 Complex at 2.1 Å", Biochemistry (2021)

Research Group