My research has been devoted to biochemical and biophysical analysis of various parts of higher plant chloroplasts. Primer focus is on the protein complex PSII, how the oxygen is produced and how the protein matrix in and around the complex is arranged for optimal electron transport for photosynthesis. Another focus is on the thylakoid lumen a chloroplast compartment that we have shown by proteomic analysis to contain a specific proteome with 40-80 proteins of which many still have unknown functions.

Wolfgang Schröder Photo: Thomas Kieselbach

Half of the proteins found in Photosystem II supercomplex are low molecular mass proteins with masses below 10kDa. The challenging question we are trying to answer is: Why does this complex have so many small subunits? We have focused on the nuclear encoded low molecular mass proteins PsbW, X, Y and Tn

With respect to the PsbW protein we have shown that it is important for the assembly of the PSII complexes, especially the docking of the LHCII antennae trimer to the complex.  However, for several other low molecular mass proteins their functions still remains unclear. To address this question we now use knock-out mutations in combination with structural analysis by cryo-EM and biophysical analysis such as single molecule spectroscopy (SMS) techniques including FCS, FLIM and FRET. The later techniques enable also analysis of molecular movements of antennae proteins in the thylakoid membrane and tagged proteins in the lumen.

The work is performed mainly on Arabidopsis plants, but we also use meristematic cell line of Arabidopsis. In these “stem cell” like cell lines, all cells are developmentally well-synchronized, and no roots, leaves or stems are differentiated. The greening process in these cell lines are slowed down from some hours to 10 days, which enable us to identify and isolate sub complexes of PSII and interaction of chaperone proteins involved in the assembly and regulatory processes and how lumen located protein interact with the membrane complexes.

Left: Greening meristematic cell line of arabidopsis; right: protein structure of photosystem II Left: Greening meristematic cell line of Arabidopsis; right: Our Cryo-EM protein structure of Arabidopsis photosystem II at 3.6Å

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