Structural and functional analyses of photosystem II in the marine diatom Phaeodactylum tricornutum release_wkvqlfgxizh33fawo2ijbhqrpm

by 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

Abstract

<jats:p>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.</jats:p>
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Published in Proceedings of the National Academy of Sciences of the United States of America by Proceedings of the National Academy of Sciences
ISSN-L 0027-8424
Page(s) 201906726
Release Date 2019-08-13
Container Type proceedings
Publisher Proceedings of the National Academy of Sciences
Primary Language en (lookup)

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Type  article-journal
Stage   published
Date   2019-08-13
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ISSN-L:  0027-8424
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