Structural variability of plant photosystem II megacomplexes in thylakoid membranes.
Plant photosystem II (PSII) is organized into large supercomplexes with variable levels of membrane-bound light-harvesting proteins (LHCIIs). The largest stable form of the PSII supercomplex involves four LHCII trimers, which are specifically connected to the PSII core dimer via monomeric antenna proteins. The PSII supercomplexes can further interact in the thylakoid membrane, forming PSII megacomplexes. So far, only megacomplexes consisting of two PSII supercomplexes associated in parallel have been observed. Here we show that the forms of PSII megacomplexes can be much more variable. We performed single particle electron microscopy (EM) analysis of PSII megacomplexes isolated from Arabidopsis thaliana using clear-native polyacrylamide gel electrophoresis. Extensive image analysis of a large data set revealed that besides the known PSII megacomplexes, there are distinct groups of megacomplexes with non-parallel association of supercomplexes. In some of them, we have found additional LHCII trimers, which appear to stabilize the non-parallel assemblies. We also performed EM analysis of the PSII supercomplexes on the level of whole grana membranes and successfully identified several types of megacomplexes, including those with non-parallel supercomplexes, which strongly supports their natural origin. Our data demonstrate a remarkable ability of plant PSII to form various larger assemblies, which may control photochemical usage of absorbed light energy in plants in a changing environment.
Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Biophysics, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.
Lukáš
L
Nosek
Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands.
Dmitry
D
Semchonok
Electron Microscopy Group, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG, Groningen, The Netherlands.
Egbert J
EJ
Boekema
Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Biophysics, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.
Petr
P
Ilík
Centre of the Region Haná for Biotechnological and Agricultural Research, Department of Biophysics, Faculty of Science, Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic.
Roman
R
Kouřil
D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism* / Q000648:ultrastructure; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D020524:Thylakoids / Q000378:metabolism* / Q000648:ultrastructure
D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex

Arabidopsis thaliana
; clear native polyacrylamide electrophoresis; grana membrane; megacomplex; photosystem II; single particle electron microscopy