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Structure-function and regulation of photosystems

Published on 27 May 2015
​Stefano Caffarri, Rainer Hienerwadel, Colette Jungas, Tania Tibiletti (PostDoc), Aurelie Crepin (PhD)


​A unique feature of photosynthetic organisms is their capacity to use solar energy to generate complex organic compounds from simple inorganic molecules. Photosystem II and Photosystem I are important enzymes where light absorption and the first steps of chemical energy conversion take place. Since plants have a sessile life style, these photosystems need to cope very efficiently with fast environmental changes such as fluctuations in the incident light and its quality. We have a pluridisciplinary approach using biochemistry, molecular biology, steady state and time resolved spectroscopic methods to better understand the structure and function of these photosystems and to elucidate their structural adaptations and defence mechanisms to stress conditions such as excess light. For this we are using the different photosynthetic models of the laboratory (Arabidopsis, Chlamydomonas, Physcomitrella and photosynthetic bacteria).

Our research topics

  • Structure and organization of plant photosystems: purification and structural analysis of reaction centres, cores and supercomplexes from photosystem I and II.
  • Electron and proton transfer in photosystem II: using light induced or electrochemically induced FTIR difference spectroscopy and time resolved nanosecond UV-VIS spectroscopy
  • Photoprotection of photosystems: regulation of state transition; role of protein PsbS; photoprotective role of carotenoids in photosystems and isolated antenna complexes. 

Photosytem II purification by ultracentrifugation of solubilized membranes in a sucrose gradient. Photosystem II supercomplexes with different antenna size migrate at different positions and have been visualized by electron microscopy techniques. A structural model of the largest PSII supercomplex is also shown.électronique - Crédit : Stefano CAFFARRI/ AMU


Structural models of Photosystem II and Photosystem I supercomplexes viewed by the lateral and luminal side. Key core subunits of PSII (D1, D2, CP47 and CP43) and its antenna complexes (LHCII, CP24, CP26 and CP29), and core subunits of PSI (PsaA-B-C-D-E-G-H-K) and its antenna complexes (Lhca1-4 and LHCII) are shown. The position of most of the chlorophylls and carotenoids is also shown (for details, see Caffarri et al. Curr. Protein Pept. Sci.,  2014) - Crédit : Stefano CAFFARRI/ AMU



Publications on PubMed​