The reaction centre of the photounit of Rhodospirillum rubrum is anchored to the light-harvesting complex with four-fold rotational disorder |
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| Authors: | Stahlberg Henning Dubochet Jacques Vogel Horst Ghosh Robin |
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| Institution: | (1) Laboratory for Ultrastructural Research (LAU), Biology Department, University of Lausanne (UNIL), CH-1015 Lausanne, Switzerland;(2) Laboratory of Physical Chemistry of Polymers and Membranes (LCPPM), Chemistry Department, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland;(3) Laboratory of Bioenergetics, University of Geneva, Ch. des Embouchis, CH-1254 Jussy-Lullier, Switzerland;(4) Department of Bioenergetics, Institute of Biology, University of Stuttgart, D-70550 Stuttgart, Germany |
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| Abstract: | The minimal photounit of the photosynthetic membranes of the purple non-sulphur bacterium Rhodospirillum rubrum, comprising the reaction centre and the light-harvesting complex has been purified and crystallised in two dimensions in the presence of added phospholipids, and subsequently visualised by electron microscopy after negatively-staining. The position of the reaction centres within the light-harvesting ring has been determined at low resolution by the application of a new analysis for rotationally disordered identical units (here the reaction centres) within a two-dimensional crystalline lattice comprised of perfectly aligned unit cells (here the light-harvesting complexes). The reaction centre was found to preferentially occupy one of four orientations within the light-harvesting complex. The light-harvesting complex appears to be distorted to C4 symmetry, thus assuming a squarish shape when visualised by negative staining. A tentative structural model of the reaction centre-light-harvesting complex photounit which fits the experimental data is proposed. |
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| Keywords: | 2D crystals image processing membrane protein structure reaction centre Rhodospirillum rubrum transmission electron microscopy |
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