in the biogenesis and turnover of the photosynthetic complexes is still limited. I focus on the photosyn- thetic light reaction with the aim to optimize plant growth for enhanced food and biomass production.
The chloroplast, an organelle with a complex architecture, consists of several distinct compartments that contain both nu- clear- and plastid-encoded proteins. Photosynthetic electron transport occurs in the thylakoid membrane, while CO2 xa- tion takes place in the stroma. In 1997 we started to develop a method for the isolation of a highly puri ed thylakoid lumen using spinach chloroplasts.We carried out the rst systemat- ic characterisation of the lumen content and showed that it contained at least 25 proteins.These data changed the common understanding of the thylakoid lumen from being mainly proton storage for the generation of the proton motive force.We were able to show that the lumen instead plays an important role in the proper function of the photosynthetic complexes and the integrity of the thylakoid membrane.
We characterised several of the novel lumen proteins. As the genome for the model organism Arabidopsis thaliana was getting available we continued our research on this organism and published the rst 2D-gels of Arabidopsis in 2000 and the complete map was published (Schubert et al. 2002). Our analysis showed that the thylakoid lumen of Arabidopsis contains at least 46 unique proteins. These include 11 immunophilins, Deg (P1, P5 and P8) proteases, 3 pentapeptiderepeat proteins, 10 PsbP domain proteins, 2 PsbQ-domain proteins, extra copies of the Photo- system II extrinsic proteins PsbO, P and Q,TL29,VDE and ve proteins with unknown function. It is thus clear that there is a very speci c group of proteins that are localized in the thylakoid lumen.The “empty” space contains proteins and thus is bound to have various enzymatic activities important for the photosynthetic process. A large program for antibody produc- tion, overexpression, crystalisation and anti-sense of these lumen proteins is now in progress.The published maps of the thylakoid lumen content are used for analysis of various stress factors such as temperature, light and nutrition. The protein changes are quanti ed with the EttanTM DIGE, and DeCyderTM image analysis platform, in combination with various MS techniques.
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