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Sci Rep. 2017 Aug 30;7(1):10067. doi: 10.1038/s41598-017-10700-8.

Pea PSII-LHCII supercomplexes form pairs by making connections across the stromal gap.

Author information

1
Applied Science and Technology Department-BioSolar Lab, Politecnico di Torino, Viale T. Michel 5, 15121, Alessandria, Italy.
2
Department of Biology, University of Padova, Via Ugo Bassi 58 B, 35121, Padova, Italy.
3
Biocomputing Unit, Centro Nacional de Biotecnología-CSIC, Darwin 3, Cantoblanco, 28049, Madrid, Spain.
4
Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152, Martinsried, Germany.
5
Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58 B, 35121, Padova, Italy.
6
ISALIT-Department of Science and Technological Innovation, University of Eastern Piedmont, Viale T. Michel 11, 15121, Alessandria, Italy.
7
Department of Science and Technological Innovation, University of Eastern Piedmont, Viale T. Michel 11, 15121, Alessandria, Italy.
8
Center for Sustainable Future Technologies - CSFT@POLITO, Istituto Italiano di Tecnologia, Corso Trento 21, 10129, Torino, Italy.
9
Applied Science and Technology Department-BioSolar Lab, Politecnico di Torino, Viale T. Michel 5, 15121, Alessandria, Italy. cristina.pagliano@polito.it.

Abstract

In higher plant thylakoids, the heterogeneous distribution of photosynthetic protein complexes is a determinant for the formation of grana, stacks of membrane discs that are densely populated with Photosystem II (PSII) and its light harvesting complex (LHCII). PSII associates with LHCII to form the PSII-LHCII supercomplex, a crucial component for solar energy conversion. Here, we report a biochemical, structural and functional characterization of pairs of PSII-LHCII supercomplexes, which were isolated under physiologically-relevant cation concentrations. Using single-particle cryo-electron microscopy, we determined the three-dimensional structure of paired C2S2M PSII-LHCII supercomplexes at 14 Å resolution. The two supercomplexes interact on their stromal sides through a specific overlap between apposing LHCII trimers and via physical connections that span the stromal gap, one of which is likely formed by interactions between the N-terminal loops of two Lhcb4 monomeric LHCII subunits. Fast chlorophyll fluorescence induction analysis showed that paired PSII-LHCII supercomplexes are energetically coupled. Molecular dynamics simulations revealed that additional flexible physical connections may form between the apposing LHCII trimers of paired PSII-LHCII supercomplexes in appressed thylakoid membranes. Our findings provide new insights into how interactions between pairs of PSII-LHCII supercomplexes can link adjacent thylakoids to mediate the stacking of grana membranes.

PMID:
28855679
PMCID:
PMC5577252
DOI:
10.1038/s41598-017-10700-8
[Indexed for MEDLINE]
Free PMC Article

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