Photosystem I of Chlamydomonas reinhardtii

Bartlomiej Drop, Mariam Birungi, Egbert J. Boekema, Fabrizia Fusetti, and Roberta Croce

Biophysical Chemistry, Molecular Photobiology,GBB,University of Groningen

Photosystem I (PSI) of Chlamydomonas reinhardtii is a large chlorophyll-binding proteins complex located in thylakoid membranes. It consists of a core complex composed of two large subunits - PsaA and PsaB, surrounded by several smaller subunits, and of a light harvesting antenna (LHCI), composed of Lhca complexes encoded by 9 genes. The exact composition of the complex and its supramolecular organization are however not known. The aim of this project is to get functional and structural information about PSI of Chlamydomonas and to test is flexibility in different environmental conditions. We were able to isolate two homogenous PSI particles with different antenna composition. Both PSI complexes were characterized and compared using absorption, low and room temperature fluorescence spectroscopy (steady state and time-resolved), pigment analysis, gel electrophoresis/mass spectrometry and single particles electron microscopy analysis. The goal is to get a comprehensive structural/functional model of PSI , which allows to relate the protein composition/organization to the functional behavior of the supercomplex.

e-mail address of presenting author: b.drop@rug.nl