Structural analysis of photosynthetic membranes by cryo-electron tomography of intact Rhodopseudomonas viridis cells |
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Authors: | Konorty Marina Kahana Nava Linaroudis Alexandros Minsky Abraham Medalia Ohad |
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Institution: | aDepartment of Organic Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel;bMax-Planck-Institute of Biochemistry, Martinsried, Germany;cThe Ben Gurion University and the NIBN, Beer Sheva 84120, Israel |
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Abstract: | During the photosynthetic process, highly organized membranal assemblies convert light into biochemical energy with high efficiency. We have used whole-mount cryo-electron tomography to study the intracellular architecture of the photosynthetic membranes of the anaerobic purple photosynthetic bacterium Rhodopseudomonas viridis, as well as the organization of the photosynthetic units within the membranes. Three-dimensional reconstruction demonstrates a continuity of the plasma membrane with the photosynthetic membranes that form tunnel-like structures with an average diameter of 31 nm ± 8 nm at the connection sites. The spacing between the photosynthetic membranes at their cytoplasmic faces was found to be 11 nm, thus enforcing a highly close packaging of the photosynthetic membranes. Analysis of successive tomographic slices allowed for derivation of the spacing between adjacent photosynthetic core complexes from a single-layered photosynthetic membrane, in situ. This analysis suggests that most, if not all, photosynthetic membranes in R. viridis are characterized by a similar two-dimensional hexagonal lattice organization. |
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Keywords: | Cryo-electron tomography Intracellular membrane organization Photosynthetic bacteria Rhodopseudomonas viridis |
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