Physiological and evolutionary implications of tetrameric photosystem I in cyanobacteria

Li, Meng; Calteau, Alexandra; Semchonok, Dmitry A.; Witt, Thomas A.; Nguyen, Jonathan; Sassoon, Nathalie; Boekema, Egbert J.; Whitelegge, Julian P.; Gugger, Muriel; Bruce, Barry D.

doi:10.1038/s41477-019-0566-x

Cited by 40 publications

(48 citation statements)

References 60 publications

(80 reference statements)

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“…Initial characterization of the thylakoid membranes of TS-821 by blue native polyacrylamide gel electrophoresis (BN-PAGE) observed a larger PSI complex ( Fig. 1A) (25). We have extended this BN-PAGE analysis using a range of 8 other common detergents, known for their ability to maintain membrane proteins in their native conformation (data not shown) where we observed the same tetrameric complex.…”

Section: Resultsmentioning

confidence: 54%

“…2D-E). However, the identity of these carotenoids could not be matched to the prior chemically identified carotenoids (25). There are a total of 362 Chl a molecules in the tetramer, 92 in monomers A and A' and 91 in monomers B and B'.…”

Section: Cofactor Placementsmentioning

confidence: 92%

“…To date, no crystal structure of the tetrameric PSI is available. Although two cryo-EM structures of the tetrameric form of PSI has been reported in a heterocyst-forming cyanobacterium, Anabaena (21,22), our lab has observed that a tetrameric PSI organization is very widespread being found in most of the Heterocyst-forming cyanobacteria and their Close Relatives (HCR) after investigating 61 different cyanobacteria (25). These organisms have been frequently proposed as the likely chloroplast progenitor (26).…”

Section: Introductionmentioning

confidence: 92%

“…Our prior work has highlighted that all or nearly all of the HCR contain a tetrameric form of PSI (21,22,25). Since previous work has shown that PsaL is driving the trimerization (32), it is not clear what determines the oligomeric state of the PSI tetrameric complex.…”

Section: Evolutionary Differences In Psalmentioning

confidence: 99%

“…Since previous work has shown that PsaL is driving the trimerization (32), it is not clear what determines the oligomeric state of the PSI tetrameric complex. However, prior work has identified changes in two regions of the PsaL primary sequence that seem to correlate with trimeric and tetrameric forms (25). To investigate that in greater details, we compared 113 PsaL orthologs from a broad range of cyanobacteria including those shown to be trimeric, far-red lightinducible Chl f-containing, marine (Prochlorococcus/Synechococcus) and putative tetrameric cyanobacteria.…”

Section: Evolutionary Differences In Psalmentioning

confidence: 99%

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Cryo-EM Structure of a Tetrameric Photosystem I from Chroococcidiopsis TS-821, a Thermophilic, Non-heterocyst-forming Cyanobacteria

Semchonok

Mondal

Cooper

et al. 2020

Preprint

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Photosystem I (PSI) is one of two the photosystems involved in oxygenic photosynthesis. PSI of cyanobacteria exists in monomeric, trimeric, and tetrameric forms, which is in contrast to the strictly monomeric form of PSI in plants and algae. The tetrameric organization raises questions about its structural, physiological, and evolutional significance. Here we report the ~3.9 Å resolution cryo-EM structure of tetrameric PSI from the thermophilic, unicellular cyanobacterium Chroococcidiopsis sp. TS-821. The structure resolves all 44 subunits and 448 cofactor molecules. We conclude that the tetramer is arranged via two different interfaces resulting from a dimer-of-dimers organization. The localization of chlorophyll molecules permits an excitation energy pathway within and between adjacent monomers. Bioinformatics analysis reveals conserved regions in PsaL subunit that correlate with the oligomeric state. Tetrameric PSI may function as a key evolutionary step between the trimeric and monomeric forms of PSI organization in photosynthetic organisms.

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Section: Resultsmentioning

confidence: 54%

Section: Cofactor Placementsmentioning

confidence: 92%