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
https://www.science.org/doi/10.1126/sciadv.abk3139