2.4 Å structure of the double concentric ringed light harvesting complex from phototrophic bacterium Gemmatimonas phototrophica

Michal Koblížek1, Alastair Gardiner1, Nupur1, Tomáš Polívka2, Niel Hunter3 and Pu Qian4

1Centre Algatech, Institute of Microbiology, Czech Academy of Sciences, 37981 Třeboň, Czechia

2Faculty of Science, University of South Bohemia, 37005 České Budějovice, Czechia

3Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield S10 2TN, UK

4Materials and Structural Analysis, Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, Netherlands


Anoxygenic photosynthesis has previously been described in the bacterial phyla; Cyanobacteria, Proteobacteria, Chlorobi, Chloroflexi, Firmicutes and Acidobacteria. Recently we described a phototrophic bacterium belonging to phylum Gemmatimonadetes [1]. This organisms Gemmatimonas phototrophica evolved the ability to use solar energy following horizontal transfer of photosynthesis-related genes from an ancient phototrophic proteobacterium.  

Thus, we used the cryo-EM technique to investigate its detailed structure. The complex contains the type-2 reaction center surrounded by two concentric rings of light harvesting antennae. The outer LH ring consist of 24 subunits and contains 72 bacteriochlorophyll (BChl) molecules. The inner ring consists of 16 subunits, with 32 BChls. The function of the light harvesting complexes was investigated using fs-spectroscopy. It was found that the LH rings serve as an energy funnel with the pigments at higher excitation energy placed at the periphery and the pigments with lower energy in the centre. The excitation energy migrates within picoseconds down the energy gradient and is finally trapped in the RC [2].


1.       Zeng, Y, Feng, F, Medová, H, Dean, J, Koblížek, M: Functional type 2 photosynthetic Reaction centers found in the rare bacterial phylum Gemmatimonadetes. Proc. Natl. Acad. Sci. USA 111: 7795-800, 2014.

2.       Qian P, Gardiner AT, Šímová I, Naydenova K, Croll TI, Jackson PJ, Nupur, Kloz M, Čubáková P, Kuzma M, Zeng Y, Castro-Hartmann P, van Knippenberg B, Goldie KN, Kaftan D, Hrouzek P, Hájek J, Agirre J, Siebert CA, Bína D, Sader K, Stahlberg H, Sobotka R, Russo CJ, Polívka T, Hunter CN, Koblížek M (2022) 2.4-Å structure of the double-ring Gemmatimonas phototrophica photosystem. Science Advances 8(7):eabk3139