ORGANIZATION · Spatial organization of photosynthetic complexes in membranes
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2004-07-01 → 2005-06-30
- EU contribution
- €40,000
- Participants
- 1
- Scheme
- ERG
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Results in brief
Final Activity Report Summary - ORGANIZATION (Spatial organization of photosynthetic complexes in membranes)
The project aims at studying the underlying mechanisms for the organisation of photosynthetic complexes in a membrane. In most photosynthetic purple bacteria, the photosynthetic apparatus consists of the Light-harvesting complexes 2 (LH2) and Light-harvesting complex 1 (LH1), which is closely associated with the photosynthetic reaction centre. In order to elucidate, which parameters are crucial for the self-organisation of the components of the photosynthetic unit in a membrane, we study the photosynthetic complexes in model membrane systems. Model membrane systems offer the advantage that parameters as the membrane composition as well as the protein concentration in the membrane can sensitively be controlled. This way, the diffusion and supramolecular assembly of the complexes can be studied as a function of different parameters, which might be crucial for an efficient organisation of the complexes in a membrane. As a model membrane system, giant unilamellar vesicles (GUV) are used. The size of GUVs (> 10 µm) significantly exceeds the optical diffraction limit and therefore allows for studying the reconstituted, autofluorescent protein complexes by fluorescence wide-field imaging. The first step in the preparation of GUVs with incorporated photosynthetic complexes comprises the reconstitution of the light-harvesting complexes into preformed large unilamellar vesicles (r ~ 70 nm) resulting in the formation of proteoliposomes. The reconstituted light-harvesting complexes were spectroscopically characterised on the ensemble and single-molecule level. In the next step, the proteoliposomes were used for the preparation of GUVs. The GUV preparation requires the formation a dry and rather homogeneous proteoliposome film. This proteoliposome film is subsequently rehydrated and subjected to an alternating electric field (electroformation technique), which was shown to facilitate the GUV formation. GUVs with a relatively high amount of LH complexes incorporated into the GUV membrane could be prepared. Formation of the vesicles and incorporation of the photosynthetic complexes into the GUV membrane was verified by fluorescence wide-field imaging. In the following step, we will employ fluorescence wide-field imaging to study the diffusion and supramolecular assembly of the light-harvesting complexes. This will be done for various conditions in order to access information about which parameters influence the membrane organisation of the photosynthetic complexes.
Data: CORDIS, © European Union
Project objective
One of the most intriguing questions in biological and biophysical research is still how proteins are spatially organized in membranes and subsequently how the organization influences the biological function of a protein in particular and of the organism in general. Also for photosynthetic organisms the membrane organization of the various photosynthetic components is far from being understood. One of the simplest photosynthetic organisms are purple bacteria. Thus they were widely used as a model system in order to understand the underlying principles of the photosynthetic process. For the photosynthetic apparatus of purple bacteria, which mostly consists of the light-harvesting complexes (LH) 2 (3), LH2 and the reaction centre (RC), some elaborated models have been proposed. But for our understanding of the photosynthetic process not only the actual organization of the pigment-protein complexes in the membrane is crucial, but also which parameters actually influence the organization of the complexes with respect to each other.The objective of the proposed project is therefore to elucidate the underlying mechanisms for the organization in the photosynthetic membrane in order to contribute to a better understanding of the photosynthetic process in general and of membrane organization in particular. We will investigate the research objective by reconstituting the components of the photosynthetic apparatus of purple bacteria in model membranes and study the organisation and dynamics in the membrane as a function of light conditions, protein concentration, membrane composition, presence of additional membrane components and temperature. For our studies we want to take advantage of the technical progress in the single-molecule field.
Original text from CORDIS.
Participants
- UNIVERSITAET BAYREUTH · BAYREUTHCoordinatorGermany
Links
Data: CORDIS, © European Union