Arrangement of Photosystem II and ATP Synthase in Chloroplast Membranes of Spinach and Pea

We used cryoelectron tomography to reveal the arrangements of photosystem II (PSII) and ATP synthase in vitreous sections of intact chloroplasts and plunge-frozen suspensions of isolated thylakoid membranes. We found that stroma and grana thylakoids are connected at the grana margins by staggered la...

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Bibliographic Details
Published in:The Plant cell 2010-04, Vol.22 (4), p.1299-1312
Main Authors: Daum, Bertram, Nicastro, Daniela, Austin, Jotham II, McIntosh, J. Richard, Kühlbrandt, Werner
Format: Article
Language:English
Subjects:
ATP
Chloroplast Proton-Translocating ATPases - chemistry
Chloroplasts
Dimers
Grana
Image Interpretation, Computer-Assisted
Light-Harvesting Protein Complexes - chemistry
Membranes
Microscopy, Electron
Peas
Photosystem II
Photosystem II Protein Complex - chemistry
Pisum sativum - enzymology
Plant cells
Plants
Protein Multimerization
Spinach
Spinacia oleracea - enzymology
Thylakoids
Thylakoids - enzymology
Trimers
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Summary:We used cryoelectron tomography to reveal the arrangements of photosystem II (PSII) and ATP synthase in vitreous sections of intact chloroplasts and plunge-frozen suspensions of isolated thylakoid membranes. We found that stroma and grana thylakoids are connected at the grana margins by staggered lamellar membrane protrusions. The stacking repeat of grana membranes in frozen-hydrated chloroplasts is 15.7 nm, with a 4.5-nm lumenal space and a 3.2-nm distance between the flat stromal surfaces. The chloroplast ATP synthase is confined to minimally curved regions at the grana end membranes and stroma lamellae, where it covers 20% of the surface area. In total, 85% of the ATP synthases are monomers and the remainder form random assemblies of two or more copies. Supercomplexes of PSII and light-harvesting complex II (LHCII) occasionally form ordered arrays in appressed grana thylakoids, whereas this order is lost in destacked membranes. In the ordered arrays, each membrane on either side of the stromal gap contains a two-dimensional crystal of supercomplexes, with the two lattices arranged such that PSII cores, LHCII trimers, and minor LHCs each face a complex of the same kind in the opposite membrane. Grana formation is likely to result from electrostatic interactions between these complexes across the stromal gap.
ISSN:1040-4651
1532-298X
DOI:10.1105/tpc.109.071431