Structural and functional analyses of photosystem II in the marine diatom Phaeodactylum tricornutum

Orly Levitan, Muyuan Chen, Xuyuan Kuang, Kuan Yu Cheong, Jennifer Jiang, Melissa Banal, Nikhita Nambiar, Maxim Y. Gorbunov, Steven J. Ludtke, Paul G. Falkowski, Wei Dai

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


A descendant of the red algal lineage, diatoms are unicellular eukaryotic algae characterized by thylakoid membranes that lack the spatial differentiation of stroma and grana stacks found in green algae and higher plants. While the photophysiology of diatoms has been studied extensively, very little is known about the spatial organization of the multimeric photosynthetic protein complexes within their thylakoid membranes. Here, using cryo-electron tomography, proteomics, and biophysical analyses, we elucidate the macromolecular composition, architecture, and spatial distribution of photosystem II complexes in diatom thylakoid membranes. Structural analyses reveal 2 distinct photosystem II populations: loose clusters of complexes associated with antenna proteins and compact 2D crystalline arrays of dimeric cores. Biophysical measurements reveal only 1 photosystem II functional absorption cross section, suggesting that only the former population is photosynthetically active. The tomographic data indicate that the arrays of photosystem II cores are physically separated from those associated with antenna proteins. We hypothesize that the islands of photosystem cores are repair stations, where photodamaged proteins can be replaced. Our results strongly imply convergent evolution between the red and the green photosynthetic lineages toward spatial segregation of dynamic, functional microdomains of photosystem II supercomplexes.

Original languageEnglish (US)
Pages (from-to)17316-17322
Number of pages7
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number35
StatePublished - Aug 27 2019

All Science Journal Classification (ASJC) codes

  • General


  • Cryo-electron tomography
  • Diatom
  • Functional absorption analysis
  • Photosystem II
  • Thylakoid membranes


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