期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 116, 期 35, 页码 17316-17322出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1906726116
关键词
diatom; photosystem II; cryo-electron tomography; thylakoid membranes; functional absorption analysis
资金
- National Institute of Health Midwest Consortium for High Resolution Cryo-electron Microscopy [U24 GM116789-01A1]
- National Science Foundation EAGER award [1558128]
- National Institute of Health [R01GM080139, P01GM121203]
- Rutgers Busch Biomedical Research Grant
- Bennett L. Smith Endowment
- China Scholarship Council [201606375128]
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [1558128] Funding Source: National Science Foundation
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 cryoelectron 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.
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