Localization of the for qE required light-harvesting complex protein LhcSR3

Elisabeth Ostendorf1, Stefanie Tietz2, Susan Hawat1, Michael Specht1, Helmut Kirchhoff2, and Michael Hippler1

1) Institute of Plant Biochemistry and Biotechnology, WWU Muenster, Hindenburgplatz 55, 48143 Muenster, Germany 2) Institute of Biological Chemistry, Washington State University, Pullman, WA 99163, USA

For oxygenic photosynthetic organisms, light is necessary for energy production but excess light can also be deleterious for the system. An immediate response to excess-light intensities in green algae and higher plants is qE, the energy-dependent part of non-photochemical quenching (NPQ). In C. reinhardtii the extent of qE closely depends on the extent of LhcSR3 protein expression (1). To further analyze LhcSR3 function for qE in C. reinhardtii, we performed nearest neighbor analyses by protein cross-linking experiments and analyzed cross-linked products via mass spectrometry. By using different cross-linker reagents we show that LhcSR3- and photosystem II (PSII)- as well as light-harvesting complex II (LHCII)- subunits are positioned in short distance to one another. Furthermore immuno-gold labeling experiments of thylakoid membranes from wild-type and mutant strains using anti-LhcSR3 specific antibodies will be presented. The data favor a model where close contact of LhcSR3 with LHCII and PSII is required for energy dissipation. (1) Peers, et al. (2009). Nature 462(7272):518-21.

e-mail address of presenting author: elisabeth.ostendorf@googlemail.com