Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Final Activity Report Summary - PHOTORINGS (Photosynthesis: What controls the membrane protein Ring Size?)

This fellowship demonstrated that the Light-harvesting (LH) integral membrane proteins from photosynthetic purple bacteria, though amongst the most widely studied, still had much to reveal.

The use of different biochemical and spectroscopic techniques showed that the LH2 complexes from purple sulphur photosynthetic bacteria exhibited a certain number of marked differences with their homologues, the LH2 from non-purple sulphur photosynthetic bacteria. In particular, the LH2 complexes from allochromatium had certain properties approaching those of LH1 complexes. This was interesting since the structures of LH2 and LH1 complexes, while based on the same principle, were very different. The association of small peptide heterodimers into closed ringed structures created all these complexes. Whereas LH1 formed rings of 16 heterodimers, LH2 complexes were made of only eight or nine heterodimers. Therefore the rings were of very different sizes. We estimated the size of the LH2 from allochromatium DSM180 and strongly suggested that it was made of 13 heterodimers, being thus intermediate in size between 'normal' LH1s and LH2s. The discovery of this new form of peptide association further opened the way to eventually understand the determining factors that guided the quaternary structure for any given light-harvesting complex.

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